It is always a good idea to change filters AND fluids immediately when buying a used vehicle. You just have no way of knowing if the previous owner took care of the truck or not. A plugged fuel filter (as an example - who knows if that is your issue) can lead to a pump failure. Pump failure can lead to EXPENSIVE injector failure. Domino effect on failures/spending.
We have already seen the poor choice in oil filter/cap - probably the previous owner. That is potentially a problem. If an OEM filter is used with a tall cap, then your lubrication oil flow and pressure is significantly reduced. This can lead to serious engine problems.
If the transmission fluid and EXTERNAL filter have had similar poor maintenance, you could be in for a big expense. Best you can do is to start good maintenance practices NOW.
Lots of videos on doing these tasks if you need the help.
Wait........so using an OEM Motorcraft oil filter is BAD?😲