1) Remove the cover (4 screws) that goes above the plate / lights
2) Each light bulb has a hemispheric plastic cover, 2 screws, remove.
3) Purchase appropiate spare bulbs, easy to find at auto parts suppliers using their catalogs or electronics advisers (abut $3.50 last time I purchased them in 2007).
4) Burned bulbs are just pulled out, new bulbs inserted.
5) Pay attention - socket in my case was partially broken (aged), if you loose it inside door will need to fish it out with a hard wire or similar.
6) Put covers back - inverse order (test before).
DR - Houston