Glad to hear you can take on electrical wiring, connectors and such with confidence.
I installed the Harman Kardon head unit with CB module on my '04 EG non-Ultra using the Boom Audio Music and Intercom Kit, p/n 77108-09. I mention this because the HK head unit came out in '06, and the BAMI kit fitment information from the MOCO said it's for '07 and newer bikes.
The installation was not difficult and everything works correctly. Just study the wiring diagrams of the model you have and compare it to what's shown on the wiring diagrams of the model you are trying to replicate. And get familiar with the parts books for the model years to confirm whethere certain connectors are the same or different; if you need connectors, pins and sockets, HD has them. Fortunately, the project is just a wiring problem, not an electronic problem requiring knowledge of resistors, capacitors, building circuits, etc.
My project is described in this thread:
http://www.hdforums.com/forum/touring-models/441244-installed-w-pics-hd-boom-audio-music-and-intercom-kit-on-04-electra-glide.html
Good luck with your research and project.
Carl