For reassembly, it is much easier to keep the PC cage out, place this cable, and then install the PC cage.

My replacement part fot the DC / Sound board was new, and did not include the RJ-11 connector and cable. From the old part, the RJ-11 port is the gray connector next to the power connector. Grasp the RJ-11 connector, and slide it off of the DC / Sound board (there is no retainer nor clips, friction holds it in place). The RJ-11 connector can then be moved to the new part, just sliding into the square cut-out next to the power connector.