Chapter 13 conversion to Chapter 7, or alternatively modify chapter 13 plan to cram down car and reduce monthly payment

I am on short term disability and am in a ch 13. I filed Ch. 7 in 2005-discharged. My 13 was suspended until I am off SDI, however, I was laid off just preivous to SDI, and my attorney says I can't modify my plan to "cram" down my car, which would reduce my monthly payment in the case that I obtain new employment once I return to work at another job. He said I could not modify the plan, but we would have to dismiss the 13 and refile a new 13 to cram down the car. I don't quite understand this approach as attorney and trustee would receive full fees again. Could my case be converted to chapter 7 if I am not able to return to work within reasonable time frame? Why can't we modify my current plan? Or, can this 13 be converted to 7 even though the 7 was discharged in 2004?