I have had good luck with my local Cole muffler. Their prices are reasonable and they did my Bronco exhaust the way I wanted it,high and tight for offroad. They even let me keep an eye on the guy and help hold a couple of pipes while he burned them in.
The riv is a nice car, and has been for many years. Sometimes I wonder what weighs more - the wiring in that car or the engine
Any of the chain places can install an aftermarket exhaust system no problem - but remember they are typically franchises so one Monroe shop might be twice as good as the one down the road. Same applies to the other brands as well.
Before you plunk your cash down, make sure they can install stainless parts because that's what you have now and it lasts significantly longer than aluminized mild steel.