Hi Dan,
The treatments last 5 minutes (give or take) I don't know if IMRT is different. I found that later in the day the waiting room was empty. I had many treatments that I was in and out in a total of 15 minutes including parking.
The treatments are completely painless. Some get two per day (1/2 strength) others only one.
Yes you should be able to drive yourself (unless you get some really strong pain meds later for the famous sore throat).
6 or 7 weeks is normal.
As for medications your Rad-Oncologist can advise you about Pilocarpine (Salagen) and Amofostine. Both are an attempt to help with salivia.
Eating before or after won't matter, I would strongly advise against eating during treatment. (They won't let you anyway

)
Getting fatigue is almost a sure bet. It is not so bad but sleeping dosn't really help. You can expect to be operating at a reduced strength during and after your last treatment. How long depends on each person, but you should start to feel better after the first week or two.
You should see your dentist BEFORE treatments start and ask for a sealant for your teeth, also floride treatments are a very good idea. There are several over-the-counter floride products. Ask your dentist. The teeth can be very badly affected by the radiation so plan to be VERY diligent with dental care.