91 Voyager - alternator replacement

My 91 has been humming along (fingers crossed) when I got the 'check engine' light on/off intermittent. I didn't really have any time to diagnose the problem as we had quests in town etc. etc.
Then I noticed the raido started to fade out but it was storming out so I thought it might be the weather as it was fine again the next day.
Well finally today I stopped the van and it wouldn't start. Got a boost to get me home but my suspicion is the alternator is bad.
So my real question is (assuming I'm right) how hard is it to change it? Looks like my biggest challenge would be dealing with the serpentine belt etc.
My battery is only a year old and I will throw a charger on it tonight.

First, with engine off put a volt meter on the battery and take a reading (should see 12.0 Volts) then get her started and take another reading (should see 14.0 Volts) if either or both readings are bad that or those parts is/are what you replace. As to degree of difficulty, depens on which engine, the 3.4 and 3,0 not bad, the 3.3 and 3.8 are a bit harder.

Thanks for the replies. I'll check the voltage but I did put a charger on the battery last night and the van started fine this morning.
It is a 3.3L engine so it looks to be a bit more challenging.
I am starting to think I may be better of taking it to a garage and have them replace it as I'm not sure how difficult it is going to be to get the belt removed and back on. I've changed alternators in other cars but that was just one little belt.
So maybe a hard question to answer but to "Remove the alternator drive belt, by relieving the tension on the dynamic tensioner".

The 3.0L sections says: "Install a 1/2 in. breaker bar in the tensioner slot. Rotate counterclockwise to release belt tension and remove poly-V belt."

So I'm a little uncertain how I release the tension on the belt. If that's something that can be answered in a post great otherwise I'll likley have to pay someone else to do it (I'll do a few searches here also - thanks again).

First, the tensioner pulley has a 15MM bolt head and you need to rotate the tensioner pulley to release belt tension and take the belt off. Next you need to remove the alternator bracket (three bolts I believe) and loosen the lowert bolt (pivot bolt) on alternator and rotate alternator toward fire wall then take B+ wire and electrical connector off and then the lower alternator (pivot bolt) off and lift the alternator off.

First, the tensioner pulley has a 15MM bolt head and you need to rotate the tensioner pulley to release belt tension and take the belt off. Next you need to remove the alternator bracket (three bolts I believe) and loosen the lowert bolt (pivot bolt) on alternator and rotate alternator toward fire wall then take B+ wire and electrical connector off and then the lower alternator (pivot bolt) off and lift the alternator off.
I did manage to get a 15mm wrench on there but I need an extension or something to give me enough leverage to move it.
My plan is to take it to a parts store, where they said they can help me verify the problem is indeed the alternator (vs starter or battery) and they will also have a special tool they will loan me to release the belt.
So, hopefully once I get the belt removed the rest will not be too difficult. My haynes manual says on the 3.3 and 3.6 engines you need to put the van on jacks and remove the alternator by taking it out from underneath the engine.
I guess if that's what it takes then it just takes me longer.
I assume when I go to put the belt back on does it just uses a spring to put it back at the right tension...

The hardest part for me ('96) was to get room to rotate the socket on the tensioner, and yes when you put te belt back on the pulley will rotate back to keep correct tension on the belt. I assumed (not always wise) that the '91 was like my '96 and alternator was top mounted, evidently yours is bottom mounted.

Made some progress. Got a serpentine belt tool and was able to remove the belt from the alternator and after a bit of work I was able to get at all the bolts I needed to remove the alternator.
Now unfortunatley I am stuck.
Mine is top mounted but there isn't room to take it out the top so the manual says "you have to slide it out the bottom between the engine and the firewall (you can't remove it from above without removing the alternator mounting bracket)".
Well I've been jiggling it this way and that for the last hour or more but it just doesn't fit as it seems to be getting hung up on one of my power steering hoses.
So I am frsutrated to say the least and do not want to start disconnecting power steering hoses so I'm starting to see what I can remove up top to try and give me enough room...

I just read on another site for a '92 you need to remove the right front splash shield so I am going to look at that and see if that helps.

Well what do you know. My wife comes out to see why it's taking so long and I explain how I'm so close but I'm about to tear it apart in my frustration and she says "Well I've neve been under a car before but let me have a look". So I say be my guest, and what do you know she just pops it out in under 2 minutes like the pit crew I've always been looking for...

Now I'll need her to install if for me!

Did you remove the alternator mounting bracket ( top bolt at rear that goes to plenum,then bolts holding outside of alternator mount bracket to alternator mount plate, then bolt holding top of alternator to mount bracket, and then remove mount bracket). Then alternaotr is pushed toward firewall and electricals disconnected and then take lower alternator pivot bolt out and she should come up and out.

Did you remove the alternator mounting bracket ( top bolt at rear that goes to plenum,then bolts holding outside of alternator mount bracket to alternator mount plate, then bolt holding top of alternator to mount bracket, and then remove mount bracket). Then alternaotr is pushed toward firewall and electricals disconnected and then take lower alternator pivot bolt out and she should come up and out.
Couldn't do it that way on my '91. The mounting bracket seems to extend down to under the power steering.
But as of today it has been replaced by taking it out underneath and all appears to be working fine.

Thanks for your suggestions.