On the 454 ForFour, depending on your trim level, you either have a lower light cluster for indicators or indicators with fog lamps. This guide covers the dual light cluster but I believe this also applies to the single light cluster as well.
Tools needed: T25 Torx bit, 581 coloured bulb for the indicator, H8 bulb for the fog lamp
One important thing to note: The indicator wire doesn't extend very far from the body and because of the exposed soldering between the wiring loom and posts in the bulb holder, these can degrade and break over time or snap off very easily if the unit or the bulb holder is roughly handled. If that happens, you are in for a world of pain to resolder these back together.