pain in the header

I purchased a racing header and my ex put it on...and then my inspection was due- he had some guy do welding to it because it wasn't going to pass inspection. The manifold opening doesn't fit my car so they welded an extra piece to it and now it's leaking. My dealership told me to fix this it would be 800$$ which I don't have and I'm not paying...I am wondering if I can just find a way to remove all the welding and put the header on in it's original form or if I have to have the welding how much should I expect to pay to get it fixed as I don't know how to weld.??