Clean it off the best you can with carb cleaner and a rag. If it is below the plug, head gasket. Above the plug valve cover gasket. Hard to see if it is all gunked up. I know a multitude of problems on a vehicle can get anyone down. If you end up selling it because of your situation I can understand it. But you know exactly what you have right now and yes it needs some work but in the end you will know everything about it. I know mine inside and out. Unfortunately these trucks don't bring a lot of money unless they are in pristine shape and it sounds like you have more into it than it may be worth in its present condition. I have kicked myself in the past by selling something I shouldn't have and replaced it with something else that had more problems than if I would have fixed the first one.
From the posts I can remember you only have some minor issues, money wise I think. Worst case, head gaskets... Some work involved but not a lot of money in parts. You'll have to time it anyway. You have good tires and it sits nice, at least in the avitar. V-6 stick, Custom Deluxe, not much there to go wrong.
Spend the 572 money on a good gas saver... Put aside what your saving in gas over driving the truck and you'll have the 572 money back in no time. Just some more of my $.02
Good Chevy's are hard to come by...