Yes you can do the compression test that way, it's always done not running. I guess if you are %100 sure you can buy everything, get machining and magna flux, new parts and labor, $1300 is not bad. If I had done that method several times and had good success and knew my numbers were correct, I would agree. But I have not. Have you? It always seems to come out more because you can't stop in the middle and those who are working for you know that too when they "quote".
Big heavy stuff on Ebay is hard to sell because of the shipping. It takes extra work to pack so as not to blow out the box. That's my experience.
