1. Just pay Cummins for the repair. Don't argue pay whatever they say and ask for a warranty on the repairs.
2. Send the claim and copy of your paid repair receipt to GoodSam for reimbursement.
3.If you don't have a check in 60 days file a suit in your local small claims court. Good sam will likely call you the minute they get a notice of suit to pay you. If not you will not only win and get your money but they will have to pay court costs too. Best thing is you don't have to hire an attorney but they do , it's the law.
I had to do this with Anthem Blue Cross. Yep a giant like that tried to screw me out of $1500. Not only did I get the money and court costs/filing fees they even gave me a couple hundred extra for "all the trouble I had".
Patience is a virtue that usually pays in cash!!!