Alternator/generator/regulator problems of the 2004 GMC Sierra 1500

I have been having trouble starting my 2004 GMC, sometime when I turned the key it would do nothing, I had it towed in and spent over $500 to repair it, alternator, battery etc, and it did not fix the problem. When I got it back, and it did it again, I found that if I moved the steering wheel up and down with the lever, it would then start. Yesterday I went out to start my truck in my driveway, and the key will not turn in the ignition. It feels like the ignition came apart or something inside. The steering wheel is not locked. It is ridiculous that I will have to pay to have this vehicle towed in again and pay to repair the ignition, when gm has been having huge problems with ignitions! I have had other problems with this vehicle to include a fire under the dash. My insurance covered it because a fuse melted and did not do it's job, however now my speedometer does not work, and they want me to pay for a new wiring harness which I will not do. I use my gps to track my speed! the rear transfer case went on it, and I spent $1,800 to have a new one installed. There have been other small things, but those are the major problems I have had over the years. I am like every other average person. I had no idea how to get gm to fix them, so I just paid myself! when I was researching how to replace the ignition, I came across your site. I have no idea what I can do about this or how to go about it. I need my truck as soon as possible, so I will probably get stuck paying again! thank you.