A regen with take about 40 miles. Any time is is stopped it will have to restart again. Go out on the highway and watch your mileage. During a regen the mileage should suck compared to what it normally is. Once the region is done the mileage will go back to normal.
As for your other question doing a delete is ok as long as you don't have any warranty left. You can bump up the power as well but then you will have to do upgrades as well including head studs and pump. Most will delete the egr as well. If your under warranty still this will void it. Go onto the duramax forums and do some research for more info.