My boyfriend and I have done this. It is a labor of love, but well worth it. INSULATE INSULATE INSULATE that sleeper area...we used foam board on the walls and BEHIND the sleeper wall. For the back and side (sleeper and cargo areas) windows we used the roll foil bubble insulation...so for the side mirrors, we added the fish-eye stick on mirrors (remember, your rearview will be useless once you build a sleeper). Insulate the cargo hold: that helps keep the sleeper area warm and quietens the ride: don't forget the roof of both cargo and sleeper! As for the doors, we popped the door pads off and put fiberglass roll insulation in those. Don't forget to wire in those auxiliary batteries and an inverter, save the primary battery's life. It's a lot of work, I am not kidding you. You will have splinters, scrapes, bruises, gashes and you will hurt in places you didn't know you had; but when it is all done, it will be a van that is way comfortable. One that you can easily hang out in Laredo for 5, 7, 10 days!