I had my engine out when I did mine, but I did a top end rebuild at the same time. The guys at the polaris shop leave the engine in.

 

If you have not done this before, I would suggest pulling the engine so you can have room to work and "see" what you are doing. It does't take much longer to go ahead and pull the engine.

 

If you're gonna tear it down, redo it all while you have it out. crank berrings as well. Go ahead and replace waterpump seals, cause I've seen them go out after time, ruin the berrings, and shell the case. It may cost a little more, but save you a lot of swearing in the long run...you'll have a fresh engine thats ready to rumble!