the check light come on atimes but not that often, forgive my ignorance (this is my first millenium beemer so im kinda like a newbie) but can the codes be checked from the car itself or do i have to go to the dealer? (they're CRAZY expensive Here!) and hw do i check the MAF?

by the way its done 45k miles and any links to helpful DIYs will be much appreciated

thanx so much for ur time!