My water pump locked up, causing the timing belt to break. That resulted in a bent valve. How expensive is this to fix, and how would i go about it?

Unless you are planning on doing the job yourself, most shops use the standard time table X their labor rate plus parts. And while they are in there, they should also do a valve job on the ones that are not obviously bent. In a shop you could spend about $1300. depending on how many valves they need to replace.