first time purchasing a truck

Ok - I completed the ppwk. to be qualified as a operator for Landstar. They'll be calling in a week(or whenever they do the ppwk) and I'll need to buy a truck.

I need some tips. I'll be a first time buyer and I am skeered, to be honest.

Where to buy? Selecttrucks or Arrow or what? Slightly used or really used? Which of the warranties should I take? I know I probably need the ones that cover the engine, tranny, and rear end, but do I want a warranty for the other stuff on the truck (starter, batteries, etc.)? How about other stuff they may offer such as that gap insurance (I guess if you get totalled and the loan is more than what the truck was worth?)? Do I need all of this stuff? Would it be worth it, even if I don't need it? Should I fill out a credit app online or go speak to them in person and then fill out the credit app? Should I get the truck inspected at like a TA or something before I buy it? How do I check the ecm mileage to make sure the odometer hasn't been rolled back?

Thanks ahead of time !!!