I went through the learning curve of taking off the bumper to replace the front indicator bulb on my 53 Ulysse and then realised that I could have done it in 5 minute with the bumper in place.
A picture is worth a thousand words as they say so, to get to the indicator bulb you need to undo he grey, round thing in the attached picture.
You have to feel around underneath the headlamp for a round hard plastic cap around 3 to 4cm diameter with two, um, wings on it, twist to unlock, then pull out with the bulb attached.
Oh and by the way, if you take out the bulb and see that there's nothing wrong with the bulb (yet the indicator is not working), the fault is almost certainly with the contacts on the side of the bulb holder itself. These often don't make good contact and the resultant sparking erodes the contact. The cure is to add a drop of solder to the contact (or replace the bulb holder with a new one). Hope this helps.