Summary: Replace Component B with EXISTING Component C in Assembly
Thanks to all that replied.
There was one method that could be done completely from Pro/Intralink, but it requires 9.1 M030 and enabling a hidden Windchill option. There was more than one method of accomplishing it with Pro/E - some quite easy and others more involved.
One of the Pro/E methods requires setting a config.pro option "let_proe_rename_pdm_objects Yes". Our "system" config.pro has this set to "No". I recommend only applying this setting to the "current session" configuration file. That way you can use it for one-off circumstances, but don't have it enabled all the time from the system or personal config.pro files.