Just put a 2 inch riser on my 97' XC 600. My throttle cable did need an extension to prevent it from crimping when the hood was closed or pulling when it was at max left/right turn.
A extension is very easy to install & it is a fairly cheap ($20) part.
Depends on your sled, but a 3 inch riser may require changes. Check to see how much slack you can get out of the wires running down your steering post, you may have to cut a zip tie or tie to get more slack.
I did end up putting a 3 inch riser on my 02 xcsp 500 and I didnt need to exstend any cables thanks for the input though, let me tell you though what a frigin differense it made riding , my wife wont drive it though she said that it feels like shes riding a chopper! :