Well I have put 1,200 miles on my 276C since posting this question. I have my answer: the 276 is still an amazing unit. As I don't have Mapsourse, I could not tell which maps I had loaded on the unit. I could tell that they were from 2008, but that was it. Turns out I have all of CA and OR on there. I made it from Arroyo Grande, Ca to McMinnville, OR guided by AAA maps and my 276. Great combo, actually. (BTW, I am riding my 2006 Buell Ulysses.)
I would still like to figure out Mapsource and get some updated maps. I know there are workarounds to the discontinued Garmin map sets. Just don't know what they are.
Anyway, I am re-dedicated to making the 276 work for me for at least a few more years.
bb