Help with header install - I'm stuck

[fmicle]

Everything was going great, I got the stock header out, had disconnected the O2 sensor, moved the donut from the stock header to the new one and started to remove the O2 sensor from the old header. It was very difficult, so I went and bought a longer wrench, so I can apply more force. After a few revolutions, just enough to see the washers inbetween moving, it got stuck. I've been trying really hard to get it moving again, but no luck. I sprayed a little W40 at the base of the bolt, but so far it hasn't helped...

Any advice? Should I try a bigger wrench? I'm slowly starting to ruin the nut with all the force. What should I do?