You are in a tricky position, I'm not sure I can offer light at the end of the tunnel.
My feeling is that the secured loan is probably at a higher interest rate so, given GMAC aren't playing ball, concentrate on clearing the secured loan. But, i just have a little worry about your husbands contribution towards clearing this faster than scheduled and maybe you should see CAB to get a bit of advice.
Once the secured loan is clear you stand a better chance of getting a better plan underway, but I think most plans would have the secured loan going first.
hope that helps a little bit
Adrian