Yep, looks like you found it.
When you take out those two little bolts (10mm? maybe) and remove that little plate, you'll find the weirdest shaped serpentire O-ring and I guess you could say a big groove in the plate, and two holes in the housing that you remove it from. In other words, the hydraulic fluid is currently coming out of one hole, through that plate, and back in the other hole, continuously circulating. You have to buy the auxilliary hydraulic outlet block (I believe that's what they called it). It will come with new, slightly longer bolts, and new O-ring, and bolts on right in place of that little plate, then it has the connections for the two hydraulic hoses. You do, of course, need an "open center" hydraulic valve because then your hydraulic fluid will be continuously circulating through that valve; a single spool if you only want hydraulic top link, two spool if you want hydraulic top link AND a hydraulic side link. I hooked mine up direct, although you can instead use quick couplers and have two pair of remotes if you have any other use for them.
Now the hydraulic fluid is currently going through that plate enroute to the 3-point hitch, so if you add the top 'n tilt, and you are extending or retracting one of those cylinders, you cannot raise the 3-point
at the same time; i.e., the new valve takes precedence over the 3-point. Of course that never bothered me because I don't have enough hands to work that many valves at once anyway.
And the 3-point will still work the same as always as long as you're not using the other valve at the same time.
