I'm looking for suggestions on cooking a whole beef tenderloin (approx 5.5
lbs) on my WSM over lump.

Basically:

-- Will this cut of meat benefit from low and slow BBQ?
-- For a chunk of meat this size I assume I can fire up the WSM using the
standard method?
-- Is there a basic guideline for cooking time / pound? I want to know how
long I should plan on smoking this baby.
-- Water in the pan?
-- Marinade, rub, both, none?

I've only had my WSM for a few weeks and have had good luck BBQ'ing turkey,
pork picnic, and ribs and even grilling some steaks, but I've never done a
piece of meat worth this much coin and I want to do it right -- I really
can't afford to experiment with these things too much, you know?

I'm willing to learn so c'mon experts -- teach me, man.

Thanks in advance everyone!