2001 39,500 miles

had some overheating probs this summer. nothing bad. noticed in late may while sitting in parking lot at work smoking a cigarette at break time with car running and A/C on that car would almost overheat in 15 mins. this is 1st year no workplace smoking laws in effect here. it sucks. it never got that hot while driving. i attributed it to the 90 degree weather. noticed again while in traffic after the F1 race in june. hot day air conditioning on and stopped and stopped more traffic. it concerned me some but but didn't happen again. i went from indy to DC and virginia coast and back in early july. no problems. took car in for oil change tonight and told dealer about overheating and to look into it. guy said they took off radiator cap and it was bubbling, which he said was a sign of a blown head gasket or a cracked head. he said i'd be fine thru the winter but next year could be real bad.

what do you think? fix it now or fix it later? and does this sound correct?