Replacing tranny is much cheaper than rebuild. Some say with a rebuild at least it's close to new again. I've heard too many stories of people getting a tranny rebuilt, and have problems shortly after. So I say get a used tranny, maybe from www.sohfast.com. They are a reputable internet used parts site. Then I would think at most $500 to swap them out (auto to auto). Put if you have a couple friends and some knowledge you could do it yourself, and save that.