My problem is the oppisite to Aaron. My light won't turn on when the passenger door opens. I'm thinking that the button switch may be bad. How hard is it to replace this switch?

just unscrew it then pull the wire off

touch the wire to ground and see if the bulb lights
if so
and if the switch just looks rusted or corroded you might get away with cleaning it up
when you take it out you will see it is a rather simple device

Dome light switch is an easy fix. First remove the fuse. Unscrew the switch from the door jamb, remove the wire clip and reinstall new switch in reverse.

removing the fuse is a good idea

but you are only closing this wire to ground to turn the light on
so it is really not needed you won't short anything out
if the wire end touches a ground it will just turn the light on

Thanks guys..

When this happened to me, it turned out to be a loose connector on the harness (the on in the trunk).