I think you'll need to pull the cluster to do what you are asking. Its not too bad to pull out. You need to undo the speedo cable from the rear of the cluster and then two connectors that go to the cluster as well. I had to pull my radio out to undo the two connectors as the cables are fairly long and plug in down that way.
Here is a picture of my cluster apart so hopefully that helps. If i recall the either the trip reset button just pulls off, or you pushed a screw driver into the opening slot seen at the bottom of it in the picture and it just pulls off.
this is helpful too
http://www.vortexbuicks-etc.com/dash_swap.htm
Once it is out everything just basically unscrews pretty easy.