Rescued my sons B but need help

Well I rescued my sons AC " B ". He had assembled it from 2 parts tractors and had it pretty much put back together when he passed away. I rescued it and 2 other tractors before they went to scrap. I installed a new wiring harness, new ignition system, and started finishing installling some other parts. The little B is now running pretty good. The B needs a little sheet metal and sheetmetal work, and it has a slight growl in the tranny but the Hydraulics needs help, and that is where I NEED HELP.
With no load or little load I can get the hydraulic cylinder to extend but I cannot get it to release except it will slowly drift back down. I mounted a plow I had around here and it will pick it up but just barely. again not able to lower it. What am I to expect when I pull the pump down? Do' s and Don'ts. I also need new linkage rods as what he had is broke or missing. Anyone have any lying around? I'm trying to get this going ASAP for a Memorial Plow Day in May for him, so I need all the help I can get and Quick. Unfortunately It will still be in its rough work cloths the first part of this year. Does this sound like stuck dirty valves or do I need to try and replace the pump? Are there rebuild kits still avaliable? What do I do, open to suggestions.