Depends on the cylinder. I've rebuilt hundreds.
Release pressure from the cylinder and look for the retaining method. Typically the barrel end (fat part) will have a screw on cap or wire retainer. PM me for more help.
BTW are we talking an electric over hydraulic press?
OK, makes more sense now.
As with many things, the value of a used Hyd. cylinder is dependant on the availability of parts for it. If a seal kit is available (or can be matched up) it is usually a very inexpensive fix.
If the cylinder is not servicable or you cannot get parts, it is a boat anchor. I'm afraid you'll have to do some digging for part #'s etc and see what is available.
