Would you be in California Bay Area -not only oil classes would be no problem, but you'd get hands on experience in muffler and differential polishing
You are on right track trying to DIY some work on the car, but bare in mind, that those cars require service that involves much more than just oil change.
You would hate to feel good changing the oil and 3 days later have brake light poping up.
I heard some institutes offer night classes in automotive maintenance so if you have no background at all you might want to start there.
And beware of help from friends. One young member did use friend for oil change on his ML320. Than he come to the forum asking why after oil change the engine runs, but the car is not moving. Reply after reply it become obvious that he has way too much motor oil in the truck, than it turned that while his friend added oil to the crankcase -he drained the transmission fluid.