Subaru Repair: Oil in coolant, subaru legacy outback, blown head gasket

Question
I have just had the oil changed on my 2000 Subaru Legacy Outback wagon (76000 miles-no prior repairs) and they said that there was oil in the antifreeze.  I am taking it to a mechanic, but can you give me an idea of what might have caused this and what the possible resolutions would be to fixing it?  Thanks.  

Answer
Hello Susan,

    The most probable cause would be a blown head gasket. Has the engine ever been overheated at any point? This will usually cause this problem. The mechanic should carefully look over the engine block to make sure there are no cracks in the cylinder walls, and check the cylinder head for cracks and warpage. The head gasket seats between the block and the head. There are 2 heads on your engine. If the block is cracked, then you will need a short block, and recommend rebuilt heads as well. Make sure they look it over really good, and I also recommend a new radiator cap. This is the most common cause of overheating. Also that engine is also noted for the LH head gasket to leak. I hope this helps you...

                                Thanks,
                                  Frank