Don't forget to take a spare belt, shovel and tow rope! I'd check track tension and alignment. Grease everything up good. Ski alignment. Anti-freeze/coolant level. Check for any visible leaks and hose condition. Check fuel line clamps and condition. Clean up the clutches. Maybe most important...make sure your sled is jetted properly for the altitudes you'll be ridding.
Have fun!

Where are you headed for to ride?