I just rebuilt the armrest on my 92 400E by myself, actually, changing the leather cover on the armrest was a piece of cake, there was a hidden clip at the back of the armrest, releasing the clip, the whole leather cover just slipped off, putting on the leather cover was also easy, all could be done in 5 minutes with bare hands, unless your 500E uses different armrest.
See thread below:
http://www.peachparts.com/shopforum/showthread.php?threadid=29222