Follow-up post-install report.
Just to give a data-point for future reference or those who come upon this thread later:
I got the replacement 206 R2.0 module, powered off the carrier, removed the dead 206, inserted the replacement unit, replaced the various line and extension modular plugs, powered up, and everything was dandy.
No programming appears to have been lost. Though, it's possible that that is because the system is running in factory-default mode already. There are 4 incoming COs and 5 extensions, with no VM or AA. I'm not familiar enough with Partner Plus / ACS to know what the default config looks like or whether the systems are usable "out of the box" without assigning CO ringing to extensions, etc. as you often must do with other systems.
Thanks for all your help & replies.
