I purchased a 1999 RMK 600 136" L/C with 864 miles, from the original owner. I took it for a test ride and it ran perfect. The exterior of the sled is like new, no scratches or paint chips, the windshield is the same. I inspected the engine compartment, it was rather dirty, oily, nothing like the exterior. The owner showed and explained the engine to me, as I have not had a sled for over 30 years. The chaincase oil needs to be changed as it really dirty, but the manual does not explain the procedure, so could someone explain that to me? Also what product is best to use to clean all of the oil and crap out of the engine compartment? Also is there anything that I should be aware of or things that I should do before putting any miles on it? Thank you in advance for sharing your knowledge!