98 Suburban - help!

I have a 98 Suburban with a 350 and 167k miles. #5 is missing - my mechanic put in a new fuel injector and it was still missing. I changed plugs, wires, cap, and rotor - still missing on #5. Back to my mechanic - checked pressure - 130 lbs, he did not check any other cylinders. He told me it may be a PCM - took it to the Chevy garage and it checked out ok. The Chevy mechanic said it's a broken valve spring. I checked out coolant and oil - down a quart of oil and a gallon of coolant, there are no leaks. I'm guessing either head gasket, cracked head, or cracked block. Regular oil changes and it's never been overheated. I want to find out what my chances are that it's a head gasket. If it's a block or head, I just want to trade it in and get something else. If I'm reasonably sure it's a head gasket, I'll have it fixed, but don't want to pay 3 to 4 hundred bucks to find out. One other thing is that it smells hot when you get out, but the gauge shows it's running on the cool side. I would appreciate an help you can provide.  

Ok. If it's a head gasket issue, you should see something on the spark plug for that cylinder. It'll look drastically different from the other plugs. Also, if you're burning coolant, you should see steam coming out of the tailpipe all the time, not just when the truck is cold and heating the moisture out of the exhuast system.

Pull the valvecover on that side and look to see if you have a broken valvespring. Stop driving the truck until you do this so you don't damage anything.