An engine repair question to the mechanics out there

[dbenamati]

I posted last week about a screw from my carb. falling in to my intake manafold and doing some damage. The screw was removed after taking my manafold off and I thought It didn't do too much damage. I was wrong. A friend stopped by to tighten and adjust valve/springs and push rods. It's not making a sloppy noise anymore but he showed me with out the vacuum gauge that my #6 has no compression (it's a 250 strait 6 cyl.) by taking off the plug wires from distributior while running. I am no mechanic and my friend does more than me but general repairs and not rebuilds. From the looks of things it is probably a bad valve or crack in the piston head to have low compression. I know the head will need pulled to find out but by doing that, what am I looking at cost wise to have that repaired? What kind of project would that turn into, have a major rebuild or just repair what's broken? My friend said he had no idea but thinks I may as well just scrap the motor. I don't know about that because first I don't have that kind of money and I kind of like my little 250-I6 and it is Original motor with 80k on it. Anyone understand where I'm comming from?

Thanks, Dave