Theoretically you could just cut the wire and splice everything together.
I actually have a XM radio antenna from my old Disco that I'm going to use as my test bed. The fantastic thing is it looks like I can actually test it on my RRS, even without a NAV-TV mod according to Woodman's guide.
I'm ordering some of the parts right now - the mini-DIN connector (which is the S-Video side), the SMB connectors, and the FAKRA connectors. I'll wire these up using some my leftover XM antenna cable. If it works - then I can order everything else.
Then if this works I'll get started on video-in-motion