Ignition Switch problems of the 2009 Chevrolet Tahoe

I have an 2009 Chevrolet Tahoe ltz that has several electrical issues. My local chevy dealer (lakeside Chevrolet in warsaw) hooked it up on their computer system and can't find anything wrong, so the dealer where I purchased this used vehicle (theautopark. Net) replaced the ignition switch because they "think" that may be what's causing my vehicle issues. Below are the various issues that I am experiencing: 1. Periodically, the door locks will cycle up and down and the power on the dash (radio, headlights, etc) goes black and the vehicle sputters like it's going to die (even while driving down the highway) 2. After that happens, and the vehicle comes out of this state, but if you smash down on the pedal the whole thing will occur again (huge safety issue while on the highway. . . No headlights and decreasing speed) 3. Sometimes, the vehicle won't start (nothing happens) 4. The cd player sounds like the motor inside is constantly running. The dealer (theautopark. Net) said this is a cooling fan. . . But it always runs? 5. The vehicle will completely die when placing the car in park and shutting off the engine (no power. . . . Nothing. Coasts to a halt. ) note: we've already replaced the battery and still have all of the aforementioned issues. Update: the ignition switch replacement was a huge fail. On the way home last night, the vehicle did some really wacky things when I used my turn signal (the vehicle slowed dramatically while driving down the highway and the headlights and dash lights flickered off and on). All of this has made me angry enough that I disconnected the battery overnight to reboot the computer. . . . I don't know if this helped or worked, but I am desperate enough to try anything right now because my family's safety is in jeopardy.