I'm with Tweed, the only way to learn this stuff is working on cheapos. And sometimes you get good/fortunate and there is a significant improvement in sound/tone. Also, there are cheapos which greatly benefit from upgrades--for instance, the Japanese instruments of the late 60s and early 70s before their luthiers got really good. I've seen some of the over braced ones come alive with their braces shaved, decent bridge plates etc. And this is very true of the Japanese electrics too-- a bridge transplant and a pickup transplant can give a very decent instrument for lower bucks. Folkies should also check out some of the Department Store and Japanese F hole models for fixer-uppers.