Ole,
Congratulations on the new bass. I own two Orions. A 5 string fretted and custom 4 string fretless.
I suggest you read the FAQ and must read sections
as there are many things there that will tell you about your new bass and how to get the best from it. To answer your questions from above:
2.
The Pan controls how much signal comes from each pickup. When in the center detent position both pickups send an equal signal to the preamp. The control
explanation can be found here.
All of the non-Series pickups are very good. They are a hum canceling style pickup. The MXY and AXY are the same except for size. The Fat Boy is optimized to be more bassy.
3.
I would not perform any upgrades right away. I would wait until you have had a chance to use the bass more. If you do decide you want to upgrade you could move to Essence electronics with a Q-switch.
You should not need to oil the body. As I recall the body is polyurethane made to look like an oil finish. All you should need to do is clean it with a good quality guitar polish.
4.
Alembic does not use foil to shield the body cavity. Instead they use conductive paint. When applied properly this gives a more complete coverage than foil.
Regards, Keith