PINOT NOIR Mystery Cache

Just a short Math test to keep you in practice, as well as to deter those who geocache just to accumulate numbers for bragging rights.

This cache is not located at the listed coordinates. Rather, the coordinates take one to a group of mailboxes. You must then follow the below instructions, using the mailbox numbers to convert the following final location of the cache into useful information:
Final Location:
     N 39 07.GHI
     W 076 00.JKL
The numbers on the black mailbox represent ABC, and those on the green mailbox represent DEF. Using this information, solve the following equations to determine the coordinates for the cache:

     G = D
     H = A - B
     I = B + E
     J = E - B
     K = (A + D) - (E + B)
     L = (A - F) - (B + E + F)

Now all that is left is to locate GZ and use your geosense to find the cache. Good Luck, and enjoy! ps: When you find the cache, look North. There is a vineyard and tasting room less than one-quarter mile away.

FTF honors go to Spitshined (who obviously wears a great pair of shoes).