Here's my two cents...
A DRW towing a heavy 5th wheel usually won't be bothered by semis and moderate wind. It is rare that I experience the type of vacuum pull when a semi goes by that I used to feel with our 23 ft. TT. The 5th wheel is very stable.
Other manuevering such as backing into a tight spot takes some practice just like it did with your MHs. Once you've done it several times it becomes second nature.
A tip that might help is to teach your DW how to tow and park the 5th wheel then she can feel for herself just how stable it is.