I'd suggest a different approach. Since your third member is already trashed, buy the parts needed to rebuild it. Buy the posi unit you want to use. Get a good book with illustrations and / or a video (they are available) and do the work yourself. Take your time. Check what you do and then recheck it again. You will learn a new valuable task. You will have this new knowledge forever. You can help others with similar conditions. You will have the bragging rights that you did it yourself.
Anyone can take it to a shop and hopefully get the job done correctly. Only some are willing to learn something new.