Re: u joint question
I am no expert and I am certain one will post here soon.
With that said... Mine made grinding noises for half of last Summer. I kept listening for the noise to get worse and it never did so I waited until Winter to change the U-joints. I could not find a thing wrong with the old ones but changed them anyway. The noise went away with the new joints, but I'm confident that I could have used the old ones for a very long time without catastrophic failure. They really are not terribly stressed like they are in a car (think about how much more torque a car applies to them), and assuming the bellows are intact, they operate in a dry and clean environment.
I think you will be fine. I would, however, recommend not turning the wheel hard under heavy power, and I'd avoid running the engine at all in the "trailer" position. No sense pushing your luck.