Diagnose extent of damage from stuck valves?

My buddys ford 460 has stuck valves. Where do I start? Could I notice anything by removing the valve covers, or do I have to remove the heads?

Is it possible to unstick them without removing the heads? Assuming they stuck from sitting.

What's the chance it bent the pushrods if it was running when they stuck? Can I check this without removing the heads? I'm not too familiar with this engine.

Stuck valves are rare in an engine like this, so must have been sitting a long time with the air cleaner off.
But they are easy to free up with penetrating oil, and working them up and down. Don't know if the piston can hit them or not. But if you pry them down with a hook on the rocker shaft, you don't have to turn the crank. If you have turned the crank and they did hit a piston, it would bend the valve and the valve would need replacing, but it would not hurt the rods.
Either way you test by pushing down on the valves to see if they move.
If they all move, then try a compression test.
Then you will know if and which ones are leaking.
May only be one head.
This tool assumes there's a rocker shaft, which I don't think there's, but maybe you can bolt up something for a tool like this to use?
http://www.ebay.com/...0940427698

A valve stuck in the open position when cranked by a starter motor can put a hole in the piston it depends on which 460 7.5L you have some are flat top some are "popups" where centers are raised i've seen both in stock motors motorhead is right you can free them but you'll wanna soak them down constantly for a week or so remember they didn't get like that over night DO NOT crank over with starter use bolt on balancer as you'll feel resistance should you encounter a stuck open valve its so much easier with heads off but you can see the guides by removing valve covers if your valves are stuck your guide seal are junk trust me