Your first guess was right--bad capacitor. He installed a generic one of the right size, and is coming back tomorrow with a "Carrier" branded one. $264 including tax. I noticed online that those parts seem to go for about $40, so next time I may have a go at it myself ("pull the power, remove cover, simple swap". He said they normally last 5-7 years and our unit is 10 years old. And yes, I DO have some idea what capacitors are capable of! : ) Although I've never handled such a large one (50.5 + 7.5). Probably still very tiny by Lew's standards.
Hmm.. I think ours goes through a pvc pipe directly down into the sewer/drainage.
Thanks! Bill