If you just bought it and the dealer ordered it, its a 2002. If it was on his lot, it could be a 2001 or 2002. The differences, well, I know of none with the possible exception of the loader control valve having a different set of parts in it.
dirt, I don't know about the serial number markings. Resale for the years 2001 to our current date will have a whole lot more to do with condition and hours then year of manufactuer. Unlike cars, very little changes with tractors. I would rather have a 2001 L48 with 300 hours then a 2002 L48 with 400 hours providing the condition was comparable. You could consider talking to Steve Carver for more information about the serial #'s, for that matter a price as well. Rat...