If these are anything like the impala/monte stepper motor issue, you can buy them cheaply on ebay/amazon and install them yourself with a little soldering
http://www.duramaxforum.com/forum/ho...r-replace.html
I replaced all 4 of my stepper motors in my 2004 Impala due to the tach needle going wonky, I will tell you it sent my heart racing while driving down the road and seeing your rpm jump to 5K while you have your foot on the accel!