Welcome to the forum!
As far as oil, you will need to buy 15q (3 five quart gallons) of Motorcraft diesel oil (CJ-4 approved). Start by changing the filter first, then drain the oil, replace the plug and refill. The plug will be a 19mm/ 3/4" socket. Replace the filter with a Motorcraft filter only. I believe the part number is FL2015- going by memory though, I could be wrong. I will let you know in a few, I am about to change my oil today. Here is a tech article that I wrote that should help you out.

https://www.ford-trucks.com/forums/9...6-0l-6-4l.html

As far as the tranny filter, I just finished doing this as well. You will need to start by removing the drain plug on the tranny pan and allow it to drain. Then, remove the tranny pan by removing the 20 bolts that hold it to the transmission. Be prepared to get oily, there will be some left in there. You will see the black plastic horn shaped filter. Pull it straight down to remove. Make sure that the orange o-ring is removed with the filter, if not then look up into the valve body and you will see the o-ring. Remove it. Install the new o-ring onto the new filter and press the filter into place until it bottoms out. Apply a little RTV and the gasket to the pan and install. Torque to specs using a cross torque pattern. Then working under the hood, remove the dipstick for the transmission (yellow handled) and fill the transmission with around 7 or 8 quarts of Mercon SP fluid. ONLY use the Mercon SP with the 5R110W transmission! It is a little hard to find, and you will probably have to get it from your Ford dealership. Start the truck and check for leaks. Then engage the truck into drive and take it on a test drive. Once at operating temperature, check the fluid level again and add more fluid as necessary. 8 quarts should do it if you are only draining the pan and not the torque converter.

Good luck!