UnbeatenPath
There have been some changes since you left,
The initial catering of the aircraft is done by the line guys in PSM. On the road for catering all the FO does is make sure that whatever the passengers use is replaced from the catering bins stored in the back of the aircraft. If they run low then the crew restocks them from catering lockers stored at 4 Plane Sense cities, or the Captain goes to a grocery store on the overnight. This happens maybe once a rotation.
We now use Foreflight which selects the route, altitude, and plans on max fuel (taking into account passengers and their bags). Before he files the flight plan the Captain selects the alternate and can modify the route, altitude, and fuel if he desires. This is no different than what I did for 22 years with my 121 airline except I don't have to coordinate with Dispatch, I just do it.
As for the lavs in my 5 years at Plane Sense all that I, or the FO, has done is removed the honey bucket from the lav and given it to the FBO line guys to dump.
I do agree with you that flying the PC-12 is very enjoyable and the most fun of my professional career.