Electrical problem
2003 GMC C2500 V8 Four Wheel Drive Automatic 99060 miles

My electrician installed a new instrument cluster and it does not display many things that are controlled by buttons on the sterring wheel. The bottom 4 buttons do not work and the mileage has started anew....and only that reads by pushing the small button on the cluster itself. It's a fully loaded duramax with full guages but most of the functions don't display . Originally the tach quit....then the speedo would drop off after a few miles and they both work well now, but the other features do not.
some of the functions that don't work are, average mileage, instant mileage, trip a, trip b, and so on.. Do I need to take this to a dealer for futher help or maybe the things just not plugged in well enough ??