This is similar to another puzzle I put there called "4th, 7th and 9th Place of Employment", GC4E7B3, but with a twist. That one has twice as many wrong Geochecker guesses as correct ones. I hope this doesn't deter the true would-be go-getters. It is going to be a challenge.
The coords at the top is not where you will find the cache. You must find the area of the attached polygon (three decimal point accuracy) without the "shaded" areas. Then multiply the result by 1000 and add 69108474. The resulting number can now be split in two and used for the last 4 digits of the north and west coords.
The difficult rating is based on the math required to solve the puzzle, not finding it. There is a 2-dollar for the first to sign this log, but you must bring your own writting utencil.
I have added a geochecker so you won't go out blind. Good Luck.
Congrats to tubatad for FTF!