The 8100 can be swapped. Technically the Geforce (64 meg version) is the best you can get for your laptop. The ATI cards (64 meg flavor) made for them were the 2nd best and Geforce 2 (16 or 32) were the 3rd best.
I really wish I could get to ebay here, I'd look at the links. You can either get them off Ebay, or order it from Dell. On second thought, Dell likely does not carry those cards anymore.
If you can post pictures of what your buying/or looking at, I should be able to confirm if it is right. BTW, I had an 8100 and swapped the GF2 for the GF4. No sweat, using Inspiron 8200 graphics drivers off dell.com. I later used Omega drivers, since I do use it for gaming. Be prepared though, your Dell WILL run hotter with a GF4 in it.
My '03 Sold.