I assume that the $5,000 is not just installation, it includes all parts and equipment. Even so it seems high, but as noted maybe not for a dealership.
Look for a mobile RV mechanic in your area. They know how to do it and it will cost about half of that.
I helped a friend install the base plate on his mini, admittedly only part of the system. It took us 4-5 hours but I could do it again in maybe 2 hours.
Brakes and lights are the big unknown as there are lots of options. With the heavier Cherokee I would definitely do brakes.