I wanna put plastic skis on my 97 polaris xc 600, and i was tryin to find out what to go with.. do 1999 rmk 700 plastic skis fit on it? are they worth 40 bucks or should I find SLP skis? or whats a good plastic ski to go with?

Yes they will fit. For $40 thats pretty cheap. There are lots of plastic skis and lots of opinions about them the best thing you can do is try to ride a sled with the skis you are interested in.