This problem could prove difficult. You should try going to your local Congressman and see if they have a Social Security trouble shooter who can help you. You also may want to check with an attorney at your local legal aid society.
I practice Social Security and Workers Compensation law in Virginia so this is not meant to be legal advice but only general information.
An overpayment can be appealed; however, if you are going to appeal it must be done within 60 days of your notice of overpayment. When you appeal an overpayment you are arguing that SSA was wrong and that you do not owe them the money back. If you are past the 60 days you can file a waiver, which can be filed at anytime. When you file a waiver you are indicating that you agree that there is an overpayment; hoewever, it was to NO fault of your own and that to ask you to repay would be a financial hardship. They will ask you for an accounting of your income and monthly expenses. A waiver can result in waiving all or a portion of the overpayment or a reasonable repayment agreement. Contacting your local legal aid or Social Security attorney would be a good idea, but don't miss the deadline for your appeal if that is what you wish to do.