Do a compression check on all the cylinders. If it seems like there is no compression, then you probably bent all the valves. The first time I bent the valves, I just bought a used head from a salvage yard, and swapped the heads, the second time, I replaced all of the valves. The valves are not an easy job to do, at least in my experience, but yes, you can replace the valves. You'll probably have indentions on the pistons, and you'll have to grind down the high spots.