i have a 96 right now with stock steelies

i plan on buying 2 sets of wheels
1 oem 5 spokes (16") what is the exact size of the oem rims. 16x?
1 set of aftermarket rims (17x7 or 17x8)

questions:
1. with the new wheels would they just be off and on?
2. im wondering if the widths (offsets) would require me to get any kind of adjustment or work?
3. is a alignment necessary afterwards as well?

 

Not sure if you're looking at 5th gen or 4th gen 16's, but the 5th gen 16's are 16" x 6.5". You won't need an alignment from simply switching rims. I have the 18" x 8" G35 18's and had no issues with fitment (using 225/45/18 tires), except that the center caps don't fit at all in the rear. Somebody else can probably help you out with the offsets, and I know there's an offset calculator out there somewhere...