That sounds OK. You could get away with holding off the first change until you have about 500 miles of heavy towing. It's easy to do, and can be done anywhere, and quickly. The diff has a drain plug, and the rear cover does not need to be removed. You may have to lower the spare to cleanly access the fill hole, though. The factory fill lube is good, it just gets full of junk. The heating/cooling cycles are key, though. Do it right and the diff will last your lifetime.