I'd take it back to the same dealer, and show them their work that you are concerned about. If they state that the work is fine, get that in writing; this way if it does fail as you fear it may, you should be covered again.
Otherwise, you'd have to locate another Jayco dealer in your area, and start again; they may not want to touch someone elses work, especially if it was done under warranty coverage.
2015 Jayco Jay Featherlight SLX16XRB (TT)
2007 Ford F150 Tow Vehicle (TV)