Oil found in the coolant tank (intermix) please help!

[Boxster_Love]

Hi....I just bought Boxster S 2006 and after I drove it for 2 days the LOW COOLANT LIGHT turned ON...I stoped and I added 1 Liter of coolant...the warning light went off but after one day a coolant leak from the right rear wheel area started to flow into the ground I opned the trunk and I found that the coolant is overflowing from the plastic cap of the expansion tank...the coolant has a strange color and consistency which later shown to be an oil-coolant intermix.....the car never showed overheat...the oil is clean no evidence of coolant in oil but only oil in the coolant. I took the car flat-bedded to the local Porsche dealer workshop...they told me that they have to change the heat exchanger (oil cooler), and ATF cooler, also they wanted to do a proper flushing of the coolant system before they can tell the reason of that intermix. The possibilities they explained that it may be a heat exchanger failure, blown head gasket, cracked cylinder head....I dont know what to do...they ask for a huge amount of money to do these preliminary tests and they warned me that if the reason was not in the oil cooler then a new engine is the only solution....please if anybody had similar problem I will be more than grateful to hear his/her advice.