I would do as Mike suggested with some slight differences:
1. Purchase all hydraulic fluids, engine oil, all filters and optionally 2 gallons of 50/50 permanent antifreeze. It's important to be sure and change the hydraulic oil and both the hydraulic and HST filters. If you didn't have an HST transmission, I'd just say to check the oil and change the main hydraulic filter. Because having clean oil is so critical to the HST, I think you should just go ahead and spend the money to completely drain and change the fluid and both filters.
Check and top off the power steering reservoir if needed.
2. Drain all fuel from the tank and change the fuel filter. Refill the tank with fresh fuel. Slightly loosen the fuel filter and bleed all the air out until only fuel spills out. This is a messy procedure, but will save you headaches with air in the fuel lines to the injectors.
Purchase or order a Mr. Funnel filter. At some later time, pour the drained fuel back into the tank after filtering it through the Mr. Funnel filter.
3. Change out the engine oil and filter.
4. Remove the outer and inner air filters. Blow out the outer filter with compressed air. The inner filter will only be replaced if it looks really dirty. This is normally a 1000 hour filter. If the outer filter is really badly gummed up or if a critter has made a home around it, it should be replaced.
5. Remove the instrument panel and use a flashlight to inspect the area inside the cowling below the steering wheel to look for rodent or wasp nests. If you see any evidence of nests, you will have to remove the cowlings completely and remove nests and do repairs.
6. Charge and check the battery. If the battery has sat idle for two years, it's probably bad and will have to be replaced. Be sure to clean the battery terminals whether the battery has to be replaced or not.
7. Optional - Drain the coolant and refill with the new antifreeze. As a minimum, drain the coolant and look at it for contamination. If it looks really good, you can put it back in. Any evidence of contamination or rust and I'd be putting in the new antifreeze.
I don't think you have to grease the tractor before starting up the engine, but a good grease job should be done before operating the tractor to do any work.
Edit: Oh yes... Check the air pressure in the tires. If you have low pressure in one of your front tires, it's easy to make a hard turn and pop it off the rim bead. It's a pain to get industrials back on the bead and aired up. It sure is easier to do an air pressure test and air up before finding out the hard way that your tire pressure was low.