As for the lights? I would suggest looking for more fuses and the 7 pin plug. A bad ground will cause this problem also.
As for the sewer hose ? You only connect one hose to dump the tanks. Open the black tank valve. After it stios flowing, open the gray valve. You will be really lucky to find anyplace that has a hose for the flush system. Never connect any hoses you use for sewer to a potable water system. If your tanks are emepty and you have access to a sewer cleanout at home you can always flush the tanks at home dumping into the mucipal sewage system. RV parts stores sell those white plastic sewer hose carriers. Or he can make his own with a piece of 4 inch sewer pipe and a cleanout fitting and a cap. Coat will be about the same either way i suspect. Mount this down under the trailer and you'll be good to go. Once the tanks are empty and valves closed, you can add two or three gallons of water to the black tank for the next use.