It's 15mm or 16mm. What you need to do is go out and buy a simple metric tool kit that has:
-Spark plug socket
It shouldn't cost more that $40.00 and will last forever if you don't lose anything. As men, we have a responsibilty to buy tools. We have to keep on buying more and more tools until we die and leave them to our children in our will.
Also: When you change the oil, you should be able to remove the filter with gloved hands if you don't have a filter wrench. You should also pre-fill the oil filter with about 1/2 qt before you put it on the engine. Only use quality filters like Motorcraft. No FRAM filters