I've never been there, but I do want to make sure you understand something about waivers. They are not as cut and dry as they appear to be. If there was gross neglegance, they are still liable, even if you did sign a waiver. Of course, this may be difficult or even impossible to prove, but a waiver doesn't cover somenoe from complete idiocy. This may not be the case for you, I dunno, but it may be worth looking into, especially if they misrepresented themsleves and their tuning abilities.
Best of luck to you.