Got it working this week-end! I would say it is back to the state it was a few years back. Just added some fluids and put her nose down.
I did not take the pressure, but I am sure the pump does not deliver its nominal 2500 psi. But for now, I can pick up the Bush Hog. When the engine is shut down, it drops to the point where the wheel touch the groung (It takes a few minutes). But then it stays there, so it is good enough for me.
For the pump, we'll propably take it out next winter to see if I can rebuild it. I want to see if the pistons are worn before doing anything else.
Thanks for the follow-ups.