I have scanned the hyd pages pages from my Massey 65 manual. They are located on my photobucket site.
They are the first images I put up so you will have to look for page 14, go to first page, download, and print. There are 26 pages in all and are in reverse order.
If I recalll correctly, first drain the oil down, pull the PTO shaft, pull the lift cover, remove the driveshaft, pull the pins and lift out the pump. It takes a while but after you do it as many times as I did, you get good at it. I had a control valve oscillator that would spin free which locked the control valve in the open position, jacking the lift arms all the way up and opening the relief on the pump. It would continue to stick until the tractor was shut off, then it would loosen up. Like you said it would work for an hour or so before this would happen. It worked well after I had the oscillator welded.
Later, my draft control would get inadvertently moved causing a no lift condition. Would scare the heck out of me til I figured it out. Now I have it locked in position so I wont bump it.