a)
make an empty hummer with mg and give it a name (hmmvee1 i.e)
make an loon which drives the Hummer, move him in as driver (see below)
make a loon which will be gunner, make sure he is NOT grouped with driver, move him in as gunner (see below)
in the init line of the Driver, besides the assignas and movein commands, put:
this setbehaviour "CARELESS"
in the init line of the gunner, besides the assignas and movein commands, put:
this setbehaviour "COMBAT"
b)
for driver: unit assignasdriver vehic; unit moveindriver vehic
for gunner: unit assignasgunner vehic; unit moveingunner vehic
for commander: unit assignascommander vehic; unit moveincommander vehic
for cargo: unit assignascargo vehic; unit moveincargo vehic
unit is the name of your loon
vehic is the name of the vehicle
basically the movein command would be enough, but your loon wont know then he is in a vehicle...can give problems when you want them to disembark.
c)
you can always use:
loon setskill 0
in the init line of a unit.