$264 for Kubota UDT-2 is an outrageous price. I get it in Arkansas for about $120. I have also read several warnings about NOT using Kubota UDT-2. Your tractor is a good sized investment. The temptation to use unbranded or off brand parts is a big one, especially when a filter cost $70 and there are several of them. But there is more at stake using parts - especially udt-2 (involves steering, transmission, loader, 4wd front and even it you have wet brakes).
I also do all my maintenance and am glad I can save the service cost. But I stay with Kubota parts and fluids. My tractor is smaller than yours L4701 - my manual says (as others have mentioned) - at 50 hours, change or check the filter for any metal and clean magnet ring if needed. Top off is udt if low. The UDT change is called for at 400 hours. Check your neighbors manual or ask him to call his Kobota dealer about the 50 hr service. Best wishes, Larry