Nate, I know you don't want to hear this, but most of the step by step is here and in dataa's pics.
You look at the YouTube vids of the P2VisionPlus upgrades to see the electric side of the work. It's just undoing 3 micro-coax connections and putting a UFL to RP-SMA pigtail on each of the empty jacks. The PS3 is actually EASIER than the P2V+ because it's all in one case and you don't have near as much disassembly.
If you open your case, you can follow the black coax line from the antenna housing to the circuit board. It's right there by the shiny arrow embossed on top of the metal shield. Follow the wire.
Then see instructions about cleaning up the goop so you can lift the jack off the board at the connection. Use tweezers to lift UP and not fingers to wiggle and hog it out. It's all in the videos.
If you found the tx antenna coax connection on the circuit board, just look an inch up and there are the two FPV jacks on the piggyback board. They all line up in a row, but the FPV are on the piggyback board. Folllow the wires back to the panel antennas up front to be sure, one gray wire, one black wire. Then you exacto the goop off those and put the UFL end of the pigtails on those. Same as in the P2V, just working in an EASIER space where it's all in the controller case.
Be REAL careful and gentle when plugging in the 3 pigtails at the UFL end. Again, see the videos. Pay attention to the what, don't worry about where in the videos.
Once you've done all 3 pigtails, the one by the arrow runs to the 5.8 RP-SMA for the flight control antenna, the piggybacked pair run to the 2.4 RP-SMA for the FPV.
Unlimited jack exit locations. Choose what suits you. Drill slowly and CAREFULLY. You do this, it's on your own--you screw up, not my fault.

If you want to exit the OEM tx antenna hole with RP-SMA, you will have to do trimming and relieving. If you can't do that, consider a different exit. Again, see the videos for suggested locations or what you need to do to relieve the antenna hole. (You need to get enough of the threaded section to stick out for antennae to screw onto).
I will post a few in process pics from last night.