Teamstew, here's a recent parallel thread. This is a fairly common problem with BX's. If you search, you can find lots of info.
Bx23 hydraulic steering failure?
You probably should rule out the steering controller before you tear into the cylinder.
I've had my cylinder apart twice now (I have 800 total hours, replaced the center o-ring @ 475, one of the side seal o-rings went bad about 100 hours ago)
I'd say I have average to above-average ability for this type of thing. For me, it was pretty much an all-day affair each time. Next time, I will probably just replace the entire unit (seems like it was around $250) and save wear and tear on my hands and patience.
It's a pain to get the cylinder removed from the tractor because of limited space to maneuver your tools, then another pain to get it apart. Attached is a couple of pages from the
BX22 WSM, the 23 is probably very similar or identical.
If you are going to go after this, I'd suggest replacing the steering hoses to and from the cylinder at the same time. The maintenance schedule calls for this every 2 years. IMO, the leak you mentioned is probably from a steering cylinder seal or maybe one of your hoses. I've replaced the hoses once, at 380 hours, when one of them split while I was running the backhoe and I lost about a gallon of fluid before I realized it. Another all-day affair. The grass has still not grown back over the spot where I was digging....