Z71 package consists of uprated torsion bars and rear springs (so it sits a little higher and rides a little rougher), 265/75R16 tires (hopefully the original tires won't still be on there by now), skid plates under the front diff and transfer case and one that goes from the frame behind the bumper to the IFS crossmember (this last one can be aluminum or plastic, try to find a metal one), Bilstein Heavy Duty shocks (which hopefully won't be on by now), the sticker, and I'm sure I'm forgetting something else.
Like u4ia4 said, if you are going to lift it, you might be better off just getting a regular 4x4 truck. Depends on the lift. With some of them all of it stays except the front skid plate, shocks, and diff skid plate. With others the only thing that is left is the stickers. If you aren't going to lift it, but still take it offroad, the Z71 is a good option. My fiance's first big American truck will probably be a Z71. Slap some 285/75R16 tires on there, build up the motor a little, and do the usual improvements, and let her have fun.
It depends on what you want to do with it.
1992 Blazer Sport, 350 TBI, 3" Flowmaster 40 DF, 4L60, K&N, Rancho 2.5" lift, 285/75R16's on 16x8 Bajas /wwwthreads_images/icons/laugh.gif