seat
Yep, tail light too. Same process on a 99 RMK. Another issue will be the cooling hoses that run under the tank and seat. I actually went to the 01 tunnel set up which runs coolant down the running boards. I have heard of guys using a heat gun on the bottom of the gen II tank to make a trough for the hoses and notching the bottom of the seat for both the hoses and tunnel cooler.
Check with Boss and Wasatch Rec and see if maybe they would change the cushion on your stock seat. May be easier.