I would like to start changing my own oil, could you tell me which plug is the oil and which is the ...

The plug form the oil is on the bottom of the oil pan (bottom of engine).

Yes, I don't believe the transmission has a plug, but if it did, it would usually be farther back on the vehicle than the oil drain plug, which is closer to the front of the vehicle since in this truck, engine and transmission are one in front of the other.