Horn Assembly problems of the 2003 Chevrolet C2500

I was traveling on the interstate with my family aboard at the speed around 75+ mph and suddenly the vehicle looses speed while traveling among others at around the same speed or higher when suddenly the speed decreases to no speed, and a this warning comes across the dash panel, that says reduced speed and all these 18 wheelers are behind me and around me. The more I press the accelerator it would do nothing but almost cost my wife a heart attack from the big trucks blowing there horn and fearing the day lights out of my family. Then a week later the cluster starts acting all crazy with the lights going out and on, and now they aren't working at all. The gauges stopped working the speed along with gas gauges etc. . . While I have never owned anything other than "chevy's", trucks and cars I have seriously been considering another name & make in my next choice of purchase. . . . So a loyal friend advised me to send gm a e-mail explaining my issues. . .