I've repaired both curl cylinders on my 30 year old Yanmar. After the local hydraulic shop charged me $165 for the first one, I did the other one myself. Its simple.
You might need to buy the specialized wrench to get the end cap off. But if it is suitable to loosen with a pipe wrench:
* I bought the HF 36" aluminum pipe wrench, for this plus I need it for plumbing repairs. It still needed a cheater pipe over it to loosen the end cap.
* Leave the opposite end of the cylinder attached on the tractor - to resist your turning force.
* Don't drop and scratch the piston rod as you pull it out.
* Disassemble the piston head from the rod. It's simply bolted on.
* Take all the removed parts to your local hydraulic shop. They will provide the seals you need, likely under $10 ~ $15. These are nearly certain to be universal generic seals, not proprietary.
* Reassemble.
* You just saved $150.