The fluid is Pentosin CHF 11s hydraulic fluid available at your friendly neighborhood NAPA dealer, and lots of other places, for less than $20 per liter. Much, much more at the Jaguar dealer.
There is not a routine service on this item. If it gets low you will feel/hear your pump moaning without any damage as long as you deal with it at that time. If the fluid is low you have a leak that is not going to get better and will need to be addressed.