Thanks Jack. Finished it all up today. I ran out and grabbed new battery cables as well. It looks like the wiring from the house side of the battery disconnect that's mounted to the side of the battery box (not sure if this is aftermarket or original) was 2AWG, but the battery cable from the disconnect to the positive terminal was 4AWG wiring.
I replaced the negative cable as well and soldered on a lug to on the chassis side of the negative to connect the shunt into the line. There is a small positive power wire to the shunt that also feeds power through the shielded cable to the monitor display inside.
I haven't gotten new batteries for the camper yet but I'm planning on getting either 2 group 24 or 27 deep cycle batteries within the next few weeks. Currently I have an old Die Hard AGM H8 battery from 2015 in there.
I checked the monitor while raising the roof - The amperage topped out at 96.1A at 11.7V for 1125W. Good info to have, for sure.
I scuffed the veneer up a little bit making the cutout but I think it looks okay otherwise.
Here's the shunt mounted along with the new batteries
I ran the wire behind the circuit breaker box and into the front floor cabinet. I passed through the floor where another wire did, and ran it into the battery box.
Overall, I'm very happy with the unit. I dry camp almost exclusively, so knowing the state of the battery is very important.
-Nick