Congrats on your new arrival, I can still remember the day when mine was delivered
To answer a few of your questions.
There have been several posters that have had great success with useing hydrostatic oil made for other tractors. As long as the label states that it is compatable with Kubota UDT you should be fine.
With that said, Kubota actually recommends you use SUDT (Super UDT) in your BX24. The main difference between UDT & SUDT is SUDT is a multiweight oil and UDT is a straight weight oil. SUDT is supposedly rated better for cold weather operation. But there have been posters that have reported no problems with UDT in the colder climates. I use SUDT but if all I could get was UDT I wouldn't hessitate to use it.
You asked in another thread if the BX24 and BX2350 were similar and YES they are. Basically, the main difference between them is the BX24 has an additional hydraulic connection & subframe added to support the backhoe. Of course the seat mount & ROPS are different but they rarely need servicing.
The engine, HST, electrics, hydraulics (except the remote BH connection) sheet metal & plastic, filters oil, etc., are all the same. They have the same FEL and MMM also.
Good luck with your new machine, it should work out very well for you.