The SE model is heavily based off the 5S model, so for a relatively close tear down, use that guide.
Most of the hardware has been upgraded from the 5S, but its a good place to start.
It may just be a connection problem of the rear camera, but the rear camera generally connects to its own socket on the logic board, so i'd suggest just starting with reseating the cable and seeing if if just happened to come loose, or possibly replacing the rear camera.
If its anything like the earlier iPhone 4 or 4S models, when dropped the most common part to receive damage was the logic boards rear camera port... so no replacement camera would work if that were the case. but hopefully the integrity of the socket is better on the later model.
i hope this helps.