Trade in a wonderful car because the battery is due for replacement? Did I read your post correctly, Paul? Are you serious?
And my friends used to accuse me of trading in cars because the ashtrays were full (before I got my MB) ...
Seriously, if this happens again, and you don't have time or transportation to buy a battery, you can always call 1-800-FOR MERC 24/7 and they'll send out a mechanic and a nice, fresh battery (and only charge you for the battery, I believe).