Probably not difficult, but installations vary so much it's difficult to say. Depends more on the particular trailer than the genset. You need to deal with the exhaust, and the fuel line if its plumbed to the RV's LP system. The latter should be simple, in any case. How does the electric power get to the trailer? Do you plug into the genset outlet, or is there some other power transfer, e.g. an auto switch? That could complicate things.
The rest should be just some bolts around the base of the genset, but getting at them could be a challenge if the trailer was built around the genset. If the genset was an add-on, then its probaby easy enough.