I think that part is still available from Cub or try one of the sponsors at the top of the page.
Yes, the valves can leak but they are easy to rebuild. I have not done one yet but here is what you will need. I think these are the same on the Cyclops machines too.
http://www.mcmaster.com/#catalog/120/3508/=tqvbnh
If your going to keep the deck lift in place you will need to add the forth valve on the other side of the machine and cut the fender pan. This link may help.
http://www.mytractorforum.com/showth...th+spool+valve
I would think if you have both lines off the cylinder you should be able to push it in and out.
Good luck in the repairs. We need some pictures.
