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The door jamb switch part price is around $12. It is just held on with a Philips screw. The switch can literally be replaced in a couple of minutes as long the the wire connector didn't fall inside the door jamb.
If the wire connector for the switch fell inside the door jamb, the hard part is to fish out the wire. Use a cost hanger making a small hook to try to fish it out.
When it first happened, I took it to a general service garage. They tried to retrieve the connectors which had also disappeared, but I think they only succeeded in pushing it further down inside.
If a shop can't fish out the wire connector from the front, they can try taking off the interior plastic B pillar lower cover off to get at it. This YouTube video shows the removal of the plastic cover. Since side impact sensors, etc. are located near here, the negative battery cable should be disconnected and waiting at least 3 minutes before starting any work.