Assuming you never bothered with a proper test drive where the handling issues would have been clearly apparent before you bought into this problem... all is not lost. The place to start is the simplest and happily also the cheapest...
Load the coach as you would for a normal trip and get to a CAT scale. Weigh the rig and take those weights to your tire manufacturers Load Inflation table. Inflate your tires for the load they are actually carrying {Ignore any sticker found in the coach and the max psi numbers on the sidewalls} and then take another test drive. Chances are good you will immediately notice a huge improvement in the ride and handling and all it cost was about $10.
If you are still having issues being pushed around by trucks and crosswinds find an alignment shop that knows trucks and RV's. You may need some additional caster with the front right needing a tad more than the left. During a proper alignment, any worn parts issues should be disclosed and you can repair or replace as needed. For a couple of hundred bucks at the high end, you have probably solved your handling issues.
"IF" you still have issues it is now time to explore aftermarket add ons that may or may not work but will undoubtedly be very expensive. Do your homework and shop wisely adding one piece at a time until you are satisfied with the overall result.
:C