Some came with carb heat and some did not...i have one that does not have it and my buddy has one that has it. I would not add it. I have almost 13,000 original miles on mine. It lets heated coolant flow around the carbs to prevent them from freezing up. I think it is used if you ride in alot of powder or follow in alot of snow dust.
At 7400 and starts on first pull, you shouldn't have to do anything but verify with a compression check. The first time I cleaned the rave valves was around 5000 miles and then again every year. Even running ski doo mineral oil they weren't that bad.
Depending on if you know the history or not of this sled, you are probably going to want to clean carbs, change out chaincase oil, go through the skid and bearings and replace any missing track clips.
These are great sleds...enjoy.