Well, I called Centerline today. It was difficult for them to give me a quote, but it sounds like the work will be somewhere in the $4000 range. Though $6000 is a heckuva price for a 03 MSP, it's more than I'm really capable of spending at this point. So, in the end, things worked for the best, and I learned a good lesson. Research BEFORE you bid! :P
But if someone wants to take my place on the project, I'm sure we could work something out.
