I think you would be better off selling the LT250r and getting used. You can find 400ex cheap and you can find a 02 raptor from $2,500 on up. Good luck!!
Now that I think of it you should keep it and just freshen up the top end. The Lt250r is a nice bike. I've never worked on one but I here 2 strokes are easy to work on and prices shouldn't be to bad. Less parts then a 4 stroke.