2003 Taurus Indicator light has us stranded... Help!

My boyfriend’s 2003 Taurus just recently had to have some serious (and expensive!) work done on it. We had a brand new transmission put in last week and it cost us $2550. We picked up the car yesterday morning and all seemed well. Now, he is stranded 2 hours from home. His car is running, but the transmission exclamation point on his dash is blinking. He doesn’t have the user’s manual and I can’t find anything online to find out if he can drive home or we have to shell out more money (!?) to fix it immediately. PLEASE, HELP!