Did one on a 99 burb a few months back, but its a 1/2 ton. Piece of cake. Cant see where yours would be any different, but I cant say for sure. Kinda tight when trying to get the new motor into the heater box, have to turn and twist to get it in there. Also, if I remember right, the bolts holding the motor in were 5.5m, which if memory serves me, I didnt have a wrench that size, only a socket. Should be a 30 min job if the 3500 is like a 1/2 ton. Everything is done from underneath by the heater box, I didnt have to tear out the dash as you suggest, but you might have a bigger job than i did.