I usually start my truck about 15 minutes prior to driving away. 1. To let the engine warm up a little, and 2. to give the heater a chance to heat it up inside. Which is a real bitch. On a cold day, it takes sometimes 30 minutes. It will heat up fast once you get goin, the exhaust brake helps alot on start up. Read your owners manual, it will tell you everything. Don't read it all at once, it will get kind of overwhelming.

On shut down, it really depends on how you drive. When I tow, I usually give it about 5 minutes at idle before I shut down. When I am just putting around town, under a minute. The reason for letting it cool down is to take the heat away from the head, at least that is what the manual says. Have fun with your truck. I have 4,000 miles on mine so far and I am pretty happy. Except for when the engine goes into REGEN because of that GD DPF!