Thanks to everyone for providing tips and links to parts companies. I am negotiating with the shop for an equitable compromise. As I mentioned in my first post, the rebuild costs $762 but the shop owner won't guarantee that problems could be uncovered which could escalate costs. I then went to one of the parts sites where I found the PS gear box for $534 which would require $300 of labor. So I offered him the latter option or cap option one at a 10% cost overrun. He balked saying that he has never worked with Importec and wouldn't want to be liable if something went wrong after the repair. I offered to sign a release of liability waiver. I believe this is fair.

I love the web, but it also makes life complicated when going through the consumer process. For example, the owner's quote for a "new" PS box is $1,128 which is the exact retail price for a remanufac box at Importec ($534 at wholesale). I then called the MB dealer and a new PS box costs $2,500. Something is fishy.