1967 580CK Boom drift - Pull the boom spool w/o removing entire control valve assy

I have a 1967 580CK with the diesel engine. Bought it a couple of years ago. The backhoe boom has had a bit of drift since I got it, but it is now to the point where when I raise it, within about a minute, the bucket will be sitting on the ground again. There is also a fair amount of leakage around the control valve area. I need to go in and check fittings to be sure they are tight, however I suspect that there is leakage in the spool (hopefully degraded seals as opposed to metal to metal wear). My question is this: Is it possible to get the spool out of the boom control valve without having to remove the backhoe and pull the entire control valve assembly? I need to do that at some point, but I was hoping to be able to do only the boom control valve right now to get the thing functioning in the short term. It is a pain to use even the front loader right now because I have to reach back and raise the boom every minute or I'll end up dragging a trench from the backhoe bucket.

Thanks, Mark

1967 580CK Boom drift - Pull the boom spool w/o removing entire control valve assy