PPL is a bit more than 500 miles from NJ. There are a number of dealers concentrated around Hershey PA along the Penna Tpke.
When buying used, a dealership with a reputation isn't really necessary. What's more important is either being able to do minor repairs and maintenance yourself, or finding a good shop locally. This is where yelp and google reviews come in. Also, visit local campgrounds and ask the manager who they call when someone at the CG needs service.
Craigslist is where most of the buying gets done.
RVT and
RVTrader have listings that you can look through to get an idea of prices that are generally 20% too high. Research CL scams before you start looking there.
Finally find an inspector to have a look at the rig before you buy. You can find a list at
NRVIA.