Fat_lazy_union and nostradamos are giving excellent advice, but I want to highlight one critical point that they’ve already brought up.
You probably have a non-recourse loan. I would advise you to get an expert third party to verify that. If true, GMAC will almost certainly want you to sign a new loan if they cut you any slack on the interest. This will almost certainly be a recourse loan. In your position, it sounds like a recourse loan would be a potential financial timebomb. DO NOT SIGN A RECOURSE LOAN UNDER ANY CIRCUMSTANCES.
As all other posters have pointed out, do not I repeat do not cash in your IRA to placate GMAC.
The time for assessing blame for getting into this loan is long past. For what it’s worth (not much), in my opinion offering these loans is the moral equivalent of giving car keys to someone who’s a staggering drunk.
