Having just done this on my car - its very easy - once you get that clip released!!
Looks like you will never get the casing off but you do need to be tugging on it when you press the metal retaining clip in. Then there are 2 small cross screws holding the indicator in -when you put the new one in you have to firmly push it into place to get it seated correctly and sealed.
Hi Davearp, i had the same problem with my C320, i don't think its the led light, because the last a long time, does your mirror folds? if they do, its most likely it a broken wire,
to gain access to the wire,first you need to fold the mirror, then with a longish screwdriver there is a hole or a opening push the scredriver in untill the spring clip move slightly back,then at the sme time, push the mirror casing out, then you will see 3 srews
holding the mirror, undo those and you should see a conector,disconect, and you should be able fined the broken wire, its quite tricky to repair, but can be done, i had to do both of mine. hope of some help.
ACMS Mercedes Ltd is an independent Mercedes-Benz service specialist based in Walsall. The company provides high levels of customer service and quality workmanship, at competitive prices. Call Mark on 01922 634666 or 07530 456000