I just had one done on my 512 loader which would be similar. Cost me 150.00 at the dealer.
Without a local Deere dealer, there a few options.
Take the cylinder to a hydraulic shop. They will be able to replace the seal (s) the leaking rod seal and the piston seal. Do both since the cylinder will be apart.
Order the parts from Deere (Google Greenfarmparts.com) and do it your self. Be aware that getting the nut off the piston can be troublesome.