It's not a terribly hard job getting it apart, it just takes some time and planning.  You'll need a fork lift or loader to support the hitch.  Keep the planter hooked to the tractor and extend the hitch all the way out.  Use the lift wheels to balance the planter so it doesn't tip forward or backward.  You'll have to take the steel plates off the side of the hitch toward the back of the square tube where it goes into the planter frame.  Then you can get inside and unbolt the plate that the back end of the cylinder hooks to and then get to the cylinder pin and pull it.  After that you can drive the tractor forward and pull the hitch out of the planter.  Be sure you have the hitch supported so it doesn't fall onto the ground.  That's as far as I've been because I had to replace the rear cylinder pin that broke.  You'll be on your own from here out, but at this point it's mostly apart.  You can surely see from here on how to get the cylinder out to fix the leak.  When you go back together you can back the tractor to push the tongue back in while using the lift wheels to line it up, higher or lower.  Be sure you drive ahead very straight so the hitch keeps straight with the planter.  It goes back in a lot better if everything is lined up.