There's probably not a dipstick on your chaincase. There will be a rubber plug on the case about 1/4 of the way from the bottom to check the level. If you have not changed the oil in a while, it's not a bad thing to do, and you can examine the chain and sprockets to see if you can identify any issues. There isn't a drain on the older sleds, either, so either fill the bellypan under the chaincase with rags or paper towels and remove the cover. The fluid will leak out onto the towels. Clean the insides with brake cleaner or WD40, put the cover back on, add 8 oz. of chaincase fluid. Done.
Or if you don't want to make a big mess, remove the exhaust. Tilt the sled on it's side, chaincase side up. Remove the cover. Use a turkey baster or other suction device and remove the oil. Check for wear/damage, put the sled back on it's track, clean, replace cover, replace fluid. It's pretty easy and should be done once a season.