Houston, we have a problem

I don't know much about yard care.  For the first time ever we have a pretty big backyard.  We have this huge old oak tree affectionately nicknamed "The House Killer".  If it comes down it's taking out our house, and quite possibly the house across the street.  The other day I went outside and noticed there were an unusual number of wasps flying around.  I went to look, and this is what I found.  These were not wasps, they are actual european hornets - about 1 1/2 inches long.  This gap in the tree is now one large hornets nest.  Uh oh.

So, I'm thinking that no one is going out back until I find an exterminator.  This isn't a knock and run deal, it's a dig the thing out of the tree.  Time to leave this to the professionals!