if you are just replacing the alternator it is actually easy. Just remove the alternator as usual (it amazing how simple the alternator removal is compared to the belt) then make sure you keep tension on the belt so it doesn't fall off of the other pulley's, a buddy helps with this. Slide your new alternator pulley under the belt and push down on the back so it sits back on it's pedestal. You can even pull up on the left side of the belt ( I believe that's the correct side) and it will pull the tensioner, making it a little easier. Once I figured it out, it was easy.
Now if you have to replace your belt, you are S.O.L. and have to cut the shroud and then bolt it back together after you are done.