The D100 is the older camera (It is from 2001); Nikon's numbering scheme is slightly confusing:
Single digit (F1, F2 D2, D3) are professional cameras
Three digit (F100, D100, D200, D300) are semi-professional cameras
Two digit (D40, D60, D90) are keen amateur cameras
Four Digit (D3000, D5000, D7000) are keen amateur cameras too
The Nikon D90 is one of the newer Nikon cameras. It comes with a detachable lens that is compatible with other Nikon lenses.
Yes, the Nikon D90 Digital SLR has image stabilization.
The Nikon D90 does have plenty of lenses, and is generally regarded as an excellent camera.
The Nikon D100 6.1 Digital SLR Camera is currently priced at $150. However, there are other Nikon D100 products that cost from about $6.99 to $200.00.
The D100 is long obsolete
Yes.
I think so
yes
yes, sure can
The Nikon D90 has plenty of lenses, but the highest one is capable of up to 35x optical zoom.
The Nikon D90 will indeed connect to a printer wirelessly, but make sure you have a compatible printer first.
Nikon stopped producing the D80 in August 2008 as it was replaced by the D90 :)