I had the same question about our old dishwasher. We rent, so we didn't want to pay for a new built-in. I found a serviceman in the local ad paper and got him over for an estimate. He seemed quite ethical to me and was totally relaxed about my haging out while he looked and tested. The estimate was quite surprisingly reasonable, so I had him go ahead.... a few hours and about 35 bucks later, I had not only a working DW new but a new element for the unworking upper oven and an evaluation of the electric cooktop's ongoing ills.
He used a combination of new and used parts, just like a good car tinker will if he can do that for you safely.
So look around and see if you can find someone reputable. Ask friends and neighbors, and realtors, who they use.