I think you just answered your own question. Pulling the heads won't cost you a thing and could tell you all you need to know. If the engine is obviously in tough shape (holed piston, scored cylinder walls, etc...), it will have cost you nothing to discover that on your own. You'll still need either a new engine or to rebuild what you have but you'll have spent notta to find that out plus look at the mad-skills you will have gained by doing that much yourself. You may then find that completing the job on your own isn't so daunting after all, at least you won't be out anything; at this point what is there to lose?