Diesel Bombers - New guy from Kansas

Hello,

I'm an almost 17 year old from Kansas, and am hopefully about to purchase my first Diesel (Dodge Cummins).

Right now, I'm looking at a 2005 Dodge 2500 Quad Cab Turbo Diesel, Auto, 4x4. after I get it, I should have about 1K-2.5K to spend on some aftermarket parts. I'm looking for some torque gains, along with acceleration.

What upgrades would you recommend to get better gas mileage, without sacrificing a lot of torque and power, or give a small boost in power and torque? I'm not wanting some full fledged 0-60 in a millisecond truck, I'd just like some umph if I need it.

Thanks!

P.S, if there's anyone around my age with close to the same truck, what are you paying for insurance? (I'm paying it all in cash up front if I get it, but I'm debating on liability or a cheap full coverage.) I've got a clean driving record from age 14 (Farmers Permit), to now. No tickets, no accidents.