Well, the Centon memory is installed and I was able to boot up with no problem - but...
Even About this Mac recognizes the module. And, no unusual behavior, although admittedly it's only been a half hour or so.
Problem is with the Hardware Test. I get an Error Code 2MLB/10/4;166, and Apple claims never to have seen this before. They suggested I download the updated Service Diagnostic and burn a copy and test the system with that. Unfortunately the GSX site is down for service...
Looks to me I'm getting what I paid for, doesn't it?
To be continued...