I would at least gut the hood and engine compartment of all the insulation and get some vents in the critical places for proper cooling of the clutches and unwanted engine heat. Cost=$150-200
The stock skis are not as bad as most make them out to be, I'd stick with them.
If you didn't get the BOSS seat, get one!
Then if you want to add some ponies, do the SLP exhaust and intake.
If you still want more! Some porting on the 800 and you really wake it up! With some CPC goodies like - a fuely box, heads, port and the twins and you'll be givin those M1K's a fit with your little light weight 800!