The only benefit I see on aftermarket exhaust is most of them use mandrel bent pipe that gives the same internal diameter all the way whereas muffler shop piping normally reduces the inner diameter in the bends.
If you get online & find a digital service manual for your year of Jeep, in the air conditioning section there is a good description & diagrams of the vacuum system in addition to some troubleshooting info.
Normally there is a small harness that runs up to the sound bar with a plastic connector that the sound bar plugs into. If the connector is different on the unit you are installing you may have to splice the wires.
On some models there is a small check valve in the washer hose. I had the Jeep in the body shop for a new hood & when they reconnected the hoses they got the check valve in backwards & no fluid would come out the nozzles.
Bought 3 temp/compass mirrors from a guy in one of the Jeep groups for $50 apiece a couple years ago. Just now installed one. Easy to install. Only problem I had was they were a little larger than stock & driver side sun visor hits it. Also went on a 99 model that had no factory harness for it...