I doubt that the NAPA filter meets the spec for the HST filter --- check the micron rating of the filter against the spec. I bought the Kubota filter for that reason.
Drain teh main tank first and replace that filter. There are then two drains under the transmission in the very back --- remove those and drain what you can. I think that I got about six gallons out total. Replace the HST filter.
I filled the main tank through the fitting on top of the tank. Once that was full, I started adding fluid through the fill port on the transmission. I used an old Tide bottle to pour from ---- it's got a nice built in funnel. Wash it out well of course. Top off the fluid level once you have it running. It's not a bad job.
