Which headers and mid pipe for my '04 GT

I'm thinking of adding headers and a new mid pipe section to my 04 GT. I already have 2 chamber flowmaster cat back system but want more sound and power. I have also installed a BBK cold air intake with stock MAF and throttle body. My question are.... I'd like to stay with shorty headers but want to know how the installation is how much fenagaling it takes to get them in there? I'm a mechanic but don't want to be tearing my car all apart to do this job. What brand headers are best? Where is the best place to buy them for the best price? Also I'd like to add high flow mid pipes. From what I'm seeing on other threads, an H-pipe will give me the deep old school sound I really like. But I only see X-pipes offered for a bolt on for my car. Also, if I get the on road with high flow cats, is there still a chance I might have my Check engine light come on? If so, I think I'll just go with off road cats, we don't have emission testing. I also saw on another thread that there is a tuner that you can shut off the rear O2 sensors off. What tuner will do this? How much are they? Are they worth it or just buy O2 simulators? Basically I want some advice on which to get and what you guys are running and how you like your set up. Will an exhaust system like this need other mods on the intake side and injectors to make it run as well as it is now? My car is only a summer time nice weather car that I'd like to bring to the drag strip this summer. Loud exhaust is ok, just not deafening. Thanks in advance.