1995 Aurora...too many headaches...need help

Alright, first off I want to say Hello since i'm a newbie hear and i've read thru basically all the topics and want to drop some feedback on my aurora before i get into the problem i am having with it.

Okay - Its a 1995 Aurora with about 90,000 miles on it.
So far i've replaced:

~ Transmission
~ New tires
~ New fuel line (finally going to get reimbursed for that)
~ Rear seat belt (from recall - thank god)
~ New battery
~ Air Flow thing (dammit i can't think of it but every so often my car would stall out b/c this 'things' hole was closed.....anyone? that was the most recent - like 3 weeks ago, works great now, starts right up and hasn't stalled since)

*there is more but those the ones that ate up my wallet*

On the flip i've added:

~ Mini Disc Stereo
~ Cd changer (10) - in the trunk in front of the arm rest which faces the front - so can change cd's at a red light (really cool suggestion for those out there)

*possible putting a flip down tv, ps2 (already have)*

Okay here is the problem i am having with it now:

~ REAR SHOCKS!!!
- i get a hissing sound as if a bag is leaking and from what i read on here its possible i need to get the MA822's.
- I'm also getting a rattle sound which sounds like its coming from my trunk but nothing is in there.

I need some help on this. I talked with a mechanic (since i'm not too good with cars but know somewhat around them) and they are saying they are going to charge 100 bucks JUST to install just the Monroe's MA822's and say its going to take at least 1/2 day. Now only that but first they'd have to charge me 20 bucks just to make sure my suspension and struts aren't part of the problem as well. I think its a bunch of b.s. and I need some help here. If anyone has a site with a diagram with play-by-play that will show me out to drop/install they new shocks (which i personally think are the problems).

PLEASE HELP ME!!!

Thanks.

Do you hear the hiss all the time & is the compressor running frequently? Verify the leak is from a strut first, maybe the air line is damaged going to a strut. Here is a link from this board with a good description on changing the rear struts in case they are bad.
http://www.automotiveforums.com/vbulletin/showthread.php?t=285183&highlight=ma822

Has anyone sat in the back seat to help localize the rattle? If your dealer replaced the seat belt retractors under warranty they would have removed the back seat and shelf (under the rear window) and maybe something is now loose under it. Also check your CD changer install in the trunk area. Inspect the rear brake pads, the inner pad material can sometimes separate from the backing plate and cause some noise (goes away when the brakes are applied). My Aurora is the same age & miles as yours and not a rattler....I track them down with a vengeance.

Good Luck!

rattle can be from a busted strut as well