Actually, sliders were originally meant to protect the exposed hard parts (case covers, etc). It's an extra benefit that manufacturers have been making them big enough that they end up protecting the plastics too.
For the reset button not working, try pressing it and holding for 10 seconds. If it still doesn't work, I'd pull the plastics and get a look at the back of the cluster. If the "select" button is working chances are it's a loose connection (hopefully). If you can't see anything obvious, then you may have to go to the dealer (still under warranty?) and leave out the part about dropping it...
For the reset button not working, try pressing it and holding for 10 seconds. If it still doesn't work, I'd pull the plastics and get a look at the back of the cluster. If the "select" button is working chances are it's a loose connection (hopefully). If you can't see anything obvious, then you may have to go to the dealer (still under warranty?) and leave out the part about dropping it...