Dash wont illuminate and other lighting issues on 99 Yukon Denalli?

1999 Yukon Denali. all my gauge light works like seat belt light and engine light but the back light wont illuminate. Someone has screwed around with it before me and my headlights are on all the time. I can turn the dimmer nob to get the dome lights on, and the dome light wont come on when the doors open. the reason i think someone has screwed around with it is because there is a wire soldered to a brown wire in the wire cluster that connects into the back of the light Control switches, the wire may or may not have something to do with the remote start that came with it.