I'm not going to give any advice on this...might get sued by one of those legal basturds!
Seriously, Evan's right, for those states following all or a significant portion of the Uniform Commercial Code (including California), there are no implied warranties that will attach to a private owner sale.
Now, to assolutely make that clear, you will want to use a typical "as-is" contractual provision. Guess what, in one of the few, very few, good things the DMV does in California, they provide you with that language in the pre-printed bill of sale available at any DMV office. I don't know about other states.
However, it never hurts to have your own contract of sale stating the same thing. Always get these things signed, and always keep a copy (or the original, if you're really on top of things
).
Like many of you, I'm more worried about lookyloos in parking lots coming up and burning their damn legs or worse. I really hate leaving a "hot" car unattended. Now that I've added front fans, I'll probably stay awake nights wondering when some moron's going to stick his hand in there, or some small dog decides to investigate while a silver-haired old lady frantically tries to pull the pureed weenie dog out...
Course, a good general liability policy never hurts.