Glad you took that in the spirit it was intended - forgot to mention, the CD I have (like the link, but for the 580B) shows a few "special tools" for working on that valve - one is a socket for removing the "float can" - the long add-on opposite the linkage end of the spool - basically, it looks like a version of one I have for those notched, round wheel bearing nuts found on some 4x4's front wheel bearings.
By now, that tool may be obsolete but if I needed one, I'd sacrifice a rarely used size of a cheap HF socket, and just grind out the space in between the "pins" that engage those slots in the end.
Dunno how desperate you are to get this going, but IIRC my CD manuals didn't take long from that vendor, and there are a few pages with decent drawings showing exactly what's gonna jump out atcha if you're not prepared :=)... Steve