I would get a rebuild done if required. Get it done by a reputable shop. Get references, Talk to the BBB see if they had many complaints.
A couple I know had a 94 Buick Park Ave. front wheel ATX. They had it done by some Backyardigan and it last 4 months! He charged them $1000 to do it. But........ you get what you pay for.
Be careful.
I wouldn't consider a used unit. You don't know what your getting. Unless you plan on unlaoding the car?