I have a Sprinter as well. During last season final average was 16.7mpg. As for towing, the Sprinter went up the grade at about 45mph and it didn't matter if the grade was 6 or 9% it just kept going.
Be careful, depending on the Jeep you could be exceeding the frame's tow capacity. NOTE: I said frame capacity, not the engine. Frame extenders and tack ons reduce the total tow weight from 5000 to 3500. It will definitely pay to know what your max weights are.
Does a little 25'er really need a tow? IMHO yes if the stay is long and there are lots of places to see/do/be. Even if its just a scooter, the ability to remain hooked up and still get around is pretty much priceless.