Dick, I made the same retro fit in my 2004 Journey 36G. The box you are looking for is 'very' difficult to find on the regular market. You can get it from Winne for a reasonable price and it fits well in the factory location.
Just be sure you have downloaded the wiring diagrams for the proper hoookup (read EMS working properly).
Also, in 2006 Winne added the refrigerator to the scheme. You can do the same by downloading the 2006 wiring diagrams and following them.
Also, you will need all the battery power you can install.
Carle McFarland, 2004 Journey 36G