Question
I live in Ellis County, Texas (North Central Texas).  I moved here in November and this spring I notice a large oak tree in my backyard is weeping.  There is a hole in the trunk and there is fluid -sap I guess coming from the trunk.  The tree at this point seems to be overall healthy lots of leaf coverage and the leaves seems to be of normal size.

Is there anything I can do myself to fix to treat this tree?

Answer
Sounds like oak borer an insect. I would spray the area on the trunk with an insecticide called Merit or Onyx. These will be absorbed into the bark and wood killing the borer under the bark. Borers usually attack trees under stress so i would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Do this now and again in the fall after leaf drop. Check with your local nursery for these insecticides.