Interesting simply because from everything I've read about MAF problems they usually don't go bad w/o giving you "warnings" first.....crappy idle, loss of power, etc.
From the dealer's perspective though, as soon as they saw that you may have been farting around with the throttle body you were toast. Do they have their labor fees posted somewhere? If not, call them before you stop by again & ask how much an hour's time is worth. Then when you go back at least you'll be armed with the knowledge or whether or not they're trying to squeeze more out of you.