Steering Column Over Drive Switch

I own a used 1998 Dodge Dakota 3.9 2WD, good condition.

The Knob on the end of the gear shift broke off, it contains the Over Drive button. The part is less then $20, but how hard is it to install and do I have to re-set the computer, when I replace it?

There is also a button to the left of the light switch, What is it for? It was pushed in when I purchased the truck. That has got to be replaced also.

That button is for the fog lights