Yes, those are the sewer hoses to dump waste water. The black (poop) tank drain is located in the left slide out, while the gray (shower) tank drain is under the generator.
Utility bodies are heavier than flat bed decks or pickup boxes.
If you are not towing, a gasoline engine will do fine to keep you moving. Even if you pack light, the truck and camper will be 15K lbs and will approach 18K lbs if you have a utility body and the camper storage filled. Add an 8K lb trailer on back like mine, and you will want a diesel.
