Did the OP even read the article that he posted to the forum. Right in the article it told you in which states you had to inform all parties.
"In 12 states (California, Connecticut, Florida, Illinois, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, Pennsylvania, and Washington) you're required to get the permission of all parties on the line before making any kind of recording. In the rest of the country, any single member that's part of the conversation can legally record it without consent from the other parties."
I live in Texas, so no worries here, but I would imagine if I lived in MA where this happened, there would be an easy workaround. If I was at the auto service center, I would have said beginning the conversation : "I need to inform you that this conversation is being recorded on an audio device."
My guess is that this gives you their consent, then the guy would have been in the clear. If you need to get their explicit permission, you could change your phrasing too : "Would you mind if I record this conversation so I can remember all the details later?"
Know your state laws, simple as that.