This is exactly the device I modded about 5 months ago - Gave it an N connector.
In the 2nd image, to the top left is a metal connector.......unsolder it. It needs to be taken off as it appears to be a test point for a special connector and switches the output to those little blue antennas on or off (on one of them anyway.)
Now, where the thing used to be, is a tiny thin track, find a good spot to solder to and solder the center of the coax to it.
Take a file, and file a big part of the ground track and use lots of flux to get solder to stick to it, and then solder the shield to this.....Voila! - You now have a modded card and the other antenna will still work in diversity mode.
If you are rangi like me, you can run the shield around the other side of the board and solder it to the big metal case on the opposing side.
Drill a few holes in the pcb in places where is doesn't matter and cable tie the coax to it - It needs LOTS of cable relief