It's pretty straight forward.
Jack up one side of your front tires.
Remove the tire.
Remove the nut on the top of the shock.
Remove the nut on the bottom of the shock.
Pull the bolt out of the bottom of the shock.
Compress the shock by hand upwards until it clears the bottom mount.(should be easy if they are nissan ones).
Once clear of the bottom mount you should be able to pull the shock out of the top mount.
Keep the bolts and nuts for the reinstall.
Here's the harder part.
Compressing the new shock. The Rancho shocks come with a wire that holds them compressed. You can use a coat hanger to do the same, but it's tougher because of the design of the Bilstein. I ended up doing it by hand.
I had success bringing the shock through the space of the a-arm behind the disc brake. Once I got the top shaft of the shock into the the mount I then compressed the shock enough to pull it into place with the bottom mount.
Put the bushings and metal discs for the top mount(I forget what they're called) in the right order and facing direction(it will be on the instructions, or just look at the order they're put on before you remove the original shocks).
Once in place, run the bottom bolt through and tighten the nut.
The top shaft (of Bilsteins) must be held in place with an Allen wrench inserted in the top of the shaft. Use a closed or open wrench to tighten the bolt down. The Bilstein instructions say not to compress the rubber bushings. (I would be curious to hear what others have done. I mentioned this to SLR and they hadn't heard of that).
The rear shocks are easy. You don't need to jack up the truck at all. It might be easier to reach the driver side shock if you remove the spare (mine is already gone).
Remove the top and bottom nuts on the shocks.
Pull the shocks off the mounts.
Put the new shock on the mounts. You'll have to compress them some. Put the metal gasket (rings) back on.
Put the nuts back on and tighten.
You might need some auto grease to lube the bushings to get them on. The Bilsteins are a tight fit.
That's pretty much it. If I forgot something, please add to the instructions. Once you do it, you'll wonder why you ever paid someone to do it for you.