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.