99 Heater O-rings

I just found some antifreeze on my passenger floor board and was informed that the Heater core O-rings (seals) are failing and the heater core is located under the dash, meaning to replace them I would have to remove a lot of dash to get to this specific location. Has anyone had this problems before? and if so has anyone attempted to repair it yourself? The dealer said they would install new O-rings for $600:eek: !!! The O-ring itself costs less then $15.00. any info would be greatly appreciated. Could I use some radiator stop leak product?

Do not use stop leak - it will plug both the heater core and radiator and cause no end of trouble.

Replacement of the o-rings is straightforward, but time consuming. It's a half-day job that requires dash disassembly, right side air bag removal, and cutting of an air duct for access. That's why they told you $600.