Could be hundreds or $1,000-$1,4000+ depending on the damage done and parts, labor, and/or machine work needed to fix! I'm assuming your timing belt is broken as that's the most common cause of bent "valves". Any fix to valves requires the removal and disassembly of the cylinder head, only 1 head if you've got the 4cyl but a V6 has 2 Cylinder Heads.
Rent it a Compression tester from auto zone or your favorite loca parts store for free, remove each spark plug individually and thread the compression tester's fitting/hose into the spark plug hole and turn the engine over & write down the compression readings from each cylinder, these numbers help determine where to go next.
Do that and let us know what you find out, we'll get you going in the right direction!
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