Earnhardt Chandler Cadillac

My CTS was at a 3rd party automotive shop for a cylinder 3 misfire code (303). Upon further inspection oil was found in the spark plug holes below the coils on all 3 left side cylinders. I was told by the 3rd party mechanic to take it to the dealer because the 100,000 mile power tran warranty was still valid and this was a bigger issue than a quick coil replacement. I had it towed to the dealership. The service writer at Earnhardt Cadillac called me and said it was $600 dollars to replace the coil (coil is only $150 of that rest is labor)and that's all it was (i knew this was obviously not true). I specifically asked him if once the mechanic took off the intake to replace the coil if any other issues were found (Like Oil!!!) would the whole service be covered...he said yes...i approved the work.. Imagine my shock when i was called shortly after and told the work was complete and ready to pick up...... (i was told by a 3rd party GM mechanic there is a quick way to cheat a rip and replace coil job by just loosening the intake and wiggling the coil out not removing the intake completely as ALLDATA says to...ALLDATA is also how they get their labor estimates from...hmmmmmm...this also blocks the mechanics view down into the cylinder/spark plug area where the oil was sitting so that's how it was not seen i assume). I asked about the oil leak and he said there was not one (firmly). I then unveiled to him that i was testing their (Earnhardt's) ethics and had had it looked at already and there was indeed a bad oil leak...he said he would call me back... He called me back and said there was a "small" oil leak but it was within General Motors Specifications to not fix....I asked him how oil filling up spark plug holes was within GM's spec's....below was his reply" "Look, your car came in here for a cylinder misfire code, we diagnosed it to be your coil...you approved the work, and that's it..." He then went on to say "Look, i've seen cars like this leak oil just like yours and sometimes it shorts the coil....but your coil is dry so it was not shorted, i also have your spark plug in my hand and there is not very much oil on it" WHAT! how is any amount of oil on a spark plug ok? not to mention he lied to me about him nor the mechanic having any knowledge of any oil leak. He then told me the car came in for a coil and he was not about to "Jeopardize his relationship with GM" over replacing a valve cover gasket that is not leaking that bad (He never saw it) I am now forced to pay 600 dollars for something that did not even fix the main issue why it was even at the dealership to begin with...earnhardt said they will not fix the oil leak because there is too much time the mechanic would have to put into it just to diagnose the problem with no guarantees....(i dont want a mechanic that takes shortcuts and overcharges working on my car anyways)...so i am having it towed on my own dime to Coulter Cadillac in Tempe where they said they would warranty the oil leak under the GM power tran 100,000 ect....