I am getting a 2019 C500S from a friend that has only 65 miles on it.  He basically bought it and used it a few times.  I am fairly sure he has done nothing with it maintenance wise.  I plan to change the oil with Maxima (30-029128 Pro Plus+ 10W-40 Synthetic oil or can I use Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil instead?   Amazon has plenty of oil filters (generic) should I use an OEM filter.

Change out the air filter with a Uni Filter NU-8503ST.

Do I need to service the diffs now?  If so what oil is recommended.

Anything else  I should be aware of that might need attention?

Riding style will ne in NEPA with mostly paved roads and some light trail riding in spring through fall.

As a side note I might add a plow - what is the best route to go with that?

I am in the market for 2 ATvs,  Thinking of CF 500-600 but hearing about part shortages, if anything goes south.  Local dealer has a bunch of them but msrp, +$1295 prep and ship,  $2% tariff and $250 "ocean ship fee"
Should I wait or pay up for a Japanese brand?