I've have the complete installation and the tank console insert is not difficult to resolve if you know someone with a Screamin Eagle Ultra. H-D will sell an insert to your friend because he can provide the VIN. Although restricted, this is not the type of part that requires the owner to send back their original part. The p/n I used is 77168-08 and it costs is about $15. I had my insert painted in the titanium color to break-up the monochromatic silver seen by the rider.
You will have two other problems to contend with: PTT switch on the left handlebar and antenna mount.
PTT is a very real and very expensive problem because H-D only offers a handlebar replacement in a black housing, and it is made for external wiring. It should be possible to remove the vinyl jacket and connector housing to run the wires inside the handlebar, but you still need to buy chrome housings and transplant the switches. Be aware that the volume control switch that comes on your SERG is centered in the chrome handlebar housing, the CB style is offset to allow room for both the volume and PTT switches, and there is a different mounting/retaining bracket for dual switches. It's putzy work.
H-D's frame mount CB antenna will disappoint you because it does not mirror the location or angle of the am/fm antenna, and interferes with the fender filler panel (requiring an access hole). All this work and it looks like you got it from JC Whitney, not H-D. I purchased another H-D am/fm (chrome) antenna bracket reversed it, drilled and tapped a hole and have a very decent solution. Send me your email, I'll see what I can do to reply with a picture.
I admire your interest in CB, it is great to be able to talk with your biker buddies.