$20b cash on hand. GM needs roughly $11b on hand for running plants, parts, etc.. Lehman estimates GM will have $12b at years end and expects capital raising during the year. It may be better holding the debt than the common.
Simple....you will fix them just like you do in third world countries.... All you need is some wire and a pair of pliers...
GM would not disappear. It would be a reorganization. Break unbearable union contracts, shed pension and health care liabilities and basically come out a lean mean fighting machine. see Kmart.
Whether or not GM disappears (I don't think it will) won't have a big impact on repairs. I own an airplane and there are dozens of models no longer manufactured that people continue to fly. Parts are readily available because there's money to be made and always someone to fill the need. I think they call it capitalism.