Read my oil filter thread in my sig, I believe the correct RP filter is part number 40-780 royal purple, double check that
here right corner.
Don't use their fluids, use ester based redline for those applications, or at least m1 as they also make some good gear fluids.
Automatic Transmission Mopar ATF+4.
This is the proper Redline c+.
Transfer Case Mopar ATF+4, Automatic Transmission Fluid.
Manual Transmission Fluid G-56 Mopar ATF+4, Automatic Transmission Fluid.
Front and Rear Axle Fluid 2500/3500 Models GL-5 SAE 75W-90 Synthetic or equivalent. 2500/3500 axles do not require limited slip additive.
This is the right gear fluid.
Check Nick at got exhaust vendor here, he literally has best pricing and shipped to door free. PM with everything you are considering, and he will give you a price, and it will likely be lower then you can get elsewhere. You can use redline engine oil, but I would look at Rotella or Delvac for the diesel. Cheapest place to get delvac is costco, and they run sales on it every other month.
Take the diffs cover off, check for metal, especially with a 2500.