I pretty much follow the book. As I recall, mine called for a 50 hour service, and then a 100 hour. I believe the 50 hour service called out changing the hydraulic fluid and filter, plus the oil and filter. I did't clean out the HST screen at that time, as I recall that is called out at the 500 hour service. Knowing what I know now, I would have cleaned it. I think it would be hard to do with out losing alot of fluid.
Was the hydraulic fluid changed at 50 hours? If not I would do it now and clean the screen while you are at it. I'm not sure how cold it gets in your location, but if it gets cold, I would use Super UDT fluid, which lets the hydraulics work a little better in the cold. I will probably stick with Kubota fluids until I'm out of warranty. Check the air filter also. If you mow alot, they get dirty quick. It's also nice to have a couple of fuel filters laying aorund also. One of mine started to plug up at around 100 hours this last winter.
Kubota sells a kit that has alot of this stuff in it. Fillters and some of the fluids all boxed up. It doesn't have enough of the fluids you will need, but it comes with a cool hat.