potentially found an 06 3500 DRW, Laramie 6spd, with 126K miles for $13,900. 00, should I be afraid because of the miles or would even be a good deal? It seems clean by the pics, in one pic there is a black box mounted under the dash on the left side that has a switch that says on/off overdrive, and what looks like a push/pull switch on the shifter???? what could that be on a 6spd???? Thanks... .....