What do I need to do to adjust the adjuster idle on my 2000 Polaris 700 SKS? I'm thinking that I need to adjust when it's running to about 1500 RPMs.

Most small engines have two screws. A big one and a small one. The big one is mixture for high speed and the small is mixture for low. Idle is a separate adjustment.

Okay... so the internet says to turn the screw 1x and the manual that my sled came with says 1 1/2 x... which would you recommend?

Usually those numbers are used to get it started. Like seat fully and back out 1.5 turns. If you have high and low speed screws then adjust each at their particular speed.