Purchase the new cable and clip.
Here is the manual showing how the cable is connected. Start at page 23.
https://www.boatmateparts.com/manuals/manual_1.pdf
There are some videos on YouTube for replacing it.
I replaced mine. I removed the swing section from the trailer so I could lay it on side to work on it. It required disconnecting the trailer wire at the swing point (5-7 pin adapter). Disconnecting the brake line from the master cylinder (lost very little fluid). When removing the pins, use wood dowels in place. this will also help when installing the assembly.
This is a thread I started. Its indirectly related. Scroll down to the last pic and you will see the dowels.
http://www.bbcboards.net/showthread.php?t=1140354&highlight=
Don