Most attorneys work on a % basis on lawsuits, so your best bet is to take all the documentation you have to a local attorney and get their advice. If you truly weren’t behind on payments, you may have some grounds for damages. There are many factors that can increase your payment, even if you are not late, including ARM’s that adjust, Pay Option Arms that reset, and increased taxes and insurance.
I am sorry to hear that you lost you home. This is one of the top ten most traumatic events that can happen to a family. I am curious however. If GMAC increased your payment, could it be that you had a ARM type loan? An ARM is an adjustable rate mortgage. This means that after an introductory period, the interest rate changes based on the market. This could make the payment increase dramatically – especially if you were making interest only payments.
Though adding escrow is a pain, the escrow amount is only equal to the existing cost of your property insurance and real estate taxes which you should have been paying anyway. If you did not have property insurance or failed to provide proof of insurance, the lender can legally put insurance on the property and their insurance is extremely expensive and could have been one reason for the increase.
Thus before pursing expensive legal counsel, I would do a little more research into some of the details to make sure that the lender was indeed practicing bad business. In this way, you will be sure of a case. Good luck!