Electrical Failure?

I must confess I am no expert on cars. My Mazda 626 started doing funny things from this morning - first the power door lock would not work unless the ignition is turned on. Then I noticed AC starts off at defogger mode (no matter how it was before) and interior lights are not working. I got the check engine light for 15 minutes, now its gone by itself. How serious is this? And how expensive?:uhoh: Should I go out of town for a 2 hour drive before fixing this or that can worsen the problem? Thanks so much.