There is no way it could be overfilled 6 quarts.....your problem is that is not the sight hole.......
If you are on the passenger side, looking at the axle coming out of the tranny, to the right of the axle opening, about 3" above the pan, is an 11mm bolt....that is the bolt you remove to check fluid level......
I normally loosen the bolt before starting the car, then make it hand tight.....the rest is like you stated...get car to normal operating temp....shift though the gears manually...put in park and keep the car running.....now remove the bolt...
Be careful.....there is a rotating belt in the area, and a hot exhaust pipe....have a pan underneath to catch the fluid dripping out.....if nothing comes out, add fluid in small increments....check to see if it dribbles out(it takes awhile when you add fluid for it to come out of that hole)....if it doesn't, add just a little more...remember, small increments....when it finally starts to dribble out, install the plug......
