you just need to run a power wire from the alternator to your battery and put a fuse or circuit breaker on it. you also need to shave the alternator bracket a little bit to clear the 3g alternator. there is a lot of write ups online
^ most junk yards have a week warranty or you can pay a little more and get a month warranty, well that's the way it is last time i went. The key is to not to buy a part and then wait along time before you install it. So when you buy a 3g alt, install it right away, that way you can return it if it doesn't work....Also alot of junk yards will mark a part that you buy will some sort of paint pen, showing that it was from there junk yard.....dont wipe that mark off until you know it works.
dap, look for a car that still has the hood on it or at least doint look like it's been sitting with no hood for a long time. spin the pully on the alt. i can spin mine, and it will continue to spin on it's own for a retarded amount of time. this is a good indicator that you found a good one.
also you need to clip of the plug you will need part of it. doint run it through the stock wiring. i used 4 gage welding cable for my charge wire(from alt to selanoid).