Ive get oil in the water dont no wat causes this

Most of the time ... a leaky gasket ( Head Gasket) Pontiac had a major recall a few years ago after DexCool in GM Engines cause gasket problems http://www.consumeraffairs.com/automotive/gm_dexcool.html

Is there any of fixing this oil is not milky so i didnt think it was a blown head gasket

I don't know of any other way for oil to get into the water .... on some cars they have a transmission cooler but your car does not show one. What the Dexcool does is it erodes the gasket between the water and oil seal ( I've personally seen it) causing oil to migrate into the cooling as the engine cools. There is usually no loss of engine performance ... the gasket remains intact at the cylinder area

So can i just replace that gasket no damage have been done to the motor right

Yes ... however replacing the Head gasket is not a waltz in the park. Try this first .... some have had success. Buy the best Head sealer ... not the cheapest ... and follow the instructions to the letter