On the question of getting axles replaced. I have read several threads about replacing axles. The process is pretty simple for any good garage mechanic. With typical power tools it should be possible to jack up a trailer, and replace the axles in 2 or 3 hours.
The only drawback is that an Airstream will not fit into most garages or go on the hoist. So they will have to do the job outdoors. No problem in good weather.
So, you might ask your local garage mechanic. It might help to print some of the pictures and descriptions so he can see what he is getting into, or the instructions provided by the manufacturer.
Living in the trailer park of sense, looking out the window at a tornado of stupidity.