problems with O2 sensor from stock header!!

[kelife]

Right now I have a very serious problem with my header O2 sensor><''! About a week ago, I bought a megan header from microimage. (wheeepeeee!!!!) I brought it directly to my frd's auto shop to do the installation! However, my frd told me the O2 sensor from the stock header was bonded too tightly against each other. He said that it might be that the manufacter overtightened the oxygen sensor initially. I saw the O2 sensor nut thingy that he was trying to take off, but he had already stripped the corners. i could tell he tried very hard to take that thingy off. I want to know if i really have to buy another O2 sensor? any places that sell OEM O2 sensor?? any1 encounter this problem when u were trying to remove the stock header?? I am very frustrated at this moment. I would appreciate it very much if you all can answer my questions ><''!!