NOPR is right. it varies state to state, and i deal with it all day at work (collections).
there are some states thats considered "dual party consent" states...California, Connecticut, Florida, Illinois, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, Pennsylvania, and Washington... basically, when we call anyone in these states, we have to tell them the call may be monitored or recorded, and continue unless they say they dont want the call recorded, in which case we have to click something to stop the recording. the remainder of the states, you can record the call without telling the other person. as long as one person knows the call is being recorded (ie, yourself), its legal. as long as the GM isnt by some odd chance in one of those states, record away
and BTW, my dads friend used to run that shop, but IIRC, he bought the tuffy at cleveland/schrock