How much will it average?

My first suspect would be the ignition control module. It's probably fried from the overheating. Check for a no spark situation. The coil packs should be tested as well. If any are weak, replace all three. The coil packs don't like to be overheated either. My 2000 Grand Prix overheated once and took out a coil pack! I'd expect the total cost to be around $500 to $700 depending on where you go for the water pump replacement and the no start diagnostics and repair. Hope that helps! Jim