overheating '04 caravan

My mom has a 2004 caravan that overheats after only 10-15 minutes driving time. I bought coolant to put in through overflow. After few days, it practically disappeared. Put more in today and really filled it, thinking it would seep into radiator. Car was not running, and after filling it up, there was a clear leak coming from that reservoir going practically into a hose right underneath it.

Don't know if it is overflow to hose that is problem. Doesn't need oil, because told it was overfilled. Don't know if thermostat, etc... Occasionally, there is a drip line left in driveway, sort of indicating left side leak. Majorly confused, and could use some help here, please

By the way, the A/C nor heat really comes up in car. As a woman, I would like to have some idea as to problem before taking to a mechanic and also potentially get taken for a ride, too.

Thanks ahead of time.

Just looking for answers, generally or specifically. My car is being serviced and need this one[as opposed to rental] for work on Tuesday. Can't travel with possibility of a breakdown.

Your overflow reservoir may be cracked.

Thanks, I thought so. Do you know approx. cost for replacement-part and labor?