I would check what your stock reciever is rated at by either asking a dealer or checking your owners manual. I say you should be fine. My opinion when pulling a trailer that is that long I would much rather have a fifth wheel than a bumper pull....less sway. Plus it distributes the weight better.
No problem. Don't worry about the mule, just load the wagon! I do pipeline work, travel alot. Had a 32 ft Jayco Eagle, pulled it on ranch hand bumper with bolt on reciever tube. New 5th wheel does pull 100% better.
In March of 2006, when I had my B&M gooseneck hitch installed, the company that did my install had several oem hitches in the showroom.
i had inquired about them and was told that I NEEDED to be very cautious
about using the factory hitch cause welds did not hold up well. I was told to stay well within the hitch towing range (read the label) on the hitch.
it's better to have a class 5, aftermarket hitch installed rather than using the
one that came installed by the factory.