You'll struggle to get the door trim off with the door shut ! If you can - there will be a plastic film covering holes in the door frame. Peel this back and you should be able to get to the mechanism. very Very tricky if not impossible with the door shut. You could try the old coathanger method to try and open the door - if your successful, then still take it apart and find out whats the matter - it sounds like something could have dislodged in the mechanism.