Under 100 might be a bit much to ask, in general the Viofo A 129 duo come in high on the list of cheap 2 channel systems.
Wires are no problem to tuck away behind plastic trim / rubber grommets / seals and the headliner. often it is a tool less deal, or at worst you will need a Phillips head screwdriver.
There are just 1 major thing, you have to be careful not routing the wire to the rear camera in front of any airbags, and it is a good idea to do a dry run first just loosely arranging the wire along the route you plan to use, just to make sure the wire are long enough.
The shortest route are often strait across the roof on top of the headliner, but this also require you have something you can "fish" the wire thru with cuz that route are probably not just a batter of pushing the wire up and over.
in general you dont have to be a rocket scientist to wire in a camera, you can also find many videos on this on youtube, maybe not for your exact brand / model of car, but they are often put together much the same in the areas you have to work with installing a camera.