Hi well, the first thing to look for, is does it have the NE5 kit on it already? 1998-2004 late production were the WC1 style, and teneded to get hot (especially in hot climates) and then develop valve seat problems.
This situation was greatly accellerated if the intake and exhaust restrictions were removed.
The kit to completely resolve those problems is 395.00 from Whiizzer Dealers, or, if no-one is near you, from WhizzeruSA in Texas. It is well to be a fair mechanic if you want to do the work yourself, otherwise find a decent mechanic for the job. There is no drilling, welding, tapping threads, no honing, just assembly (unless there is something already wrong on your engine.)
This certainly needs to be considered whan a new Whizzer is 1595.00 MSRP, and for my area the bike costs that, plus destination and local tax.
Another point to consider is that a new Whizzer will have warrantee, which can be nice.