What is customary in a tune up at Shop X will not be the same as a tune up at Shop Y. There's not that much to "tune up" on a bmx; overhaul would be different, though. Calling the shop and asking what is entailed in a bmx tune up would be the only way of actually knowing. While you've got 'em on the phone, ask about the pedal install. If they charge for the pedal install, it won't be much (just takes a few minutes). If you bought the pedals from th shop, they'd install at no charge.
