Nice to see a fellow concerned for his recruits.

Anyway, a Plant Operator is classified under the Combat Engineer arms.They operate bulldozers, excavators, forklifts and other heavy-lift equipment designed to support any Engineer exercise where trench digging and other defensive positions need to be created.
FEP operator.I have no idea, perhaps some of the Air Force guys would care to clarify?
RP and air bases and a RP at SAFPU HQ is different.The former will be under FDS(Field Defence Squadron), meaning tougher training and more infantry-like role than the one who is a SAFPU HQ, for he is merely a "service" RP.Course length is also different.