First off $550 for a timing belt job is WAY high.. i think i have heard it done for as little as $325, with a little over $400 as an average ( I do my own ). But anyhow..

This is one of those cases where i would suggest paying time to pull the head instead of getting it running on bent valves. I would get written estimates of the total job form this shop though, as the $550 timing belt job will be part of the cost of the head replacement, some of which is over lap. I would also suggest checking on their possible solutions for the machine work and valve replacement.