coolant in oil,

I took my Jeep to the car dealer to have the oil changed and was told I have coolant in my oil, the cause was a possible head gasket, and that I would need to have the motor replaced, for roughly $5,000.00.

History:
I had smelled antifreze on one occasion, about 3 or 4 weeks ago, I checked the antifrez tank, it was low, so I filled it. I have not filled it again, as it has not appeared to have gone down any. Around the 3rd of this month I started hearing a gurgling sound and I noticed that my heater was not working well. It provided heat intermitetly. on the 11th of this month, I had come back from a one hundred mile trip, (the heater worked fine and it never over heated, I had stoped for an errand, and left it running for about 45min, when I got back in to go home, the the temp said 260 I drove less than an eigthth of a mile to my home, it was turned it off within 5min. I was due for an oil change any way so I called and set an appointment for the change and want them to check the heater at the same time.

So I took my Jeep to the car dealer to have the oil changed and was told I have coolant in my oil, the cause was a possible head gasket, and that I would need to have the motor replaced, for roughly $5,000.00.

If they change the oil, and replace the head gasket(they seem to think that is the source), flush the engine, and change the oil again, will that save my engine?