Hello. You are very close by your description. Open the hood and follow the body fold up along the line from the edge of the side blinker housing. You will see a hole. You are correct that there are two ways. I think yours is the tab but it could be a screw that looks like it has a plastic housing around it. The screw one is easy as it can be seen easier, unscrew partially and then pry out gently on the marker light.
If it is the tab one then use a flashlight and look in the hole. You need a long screw driver and there is a flat tab, press down on the tab and then lever the handle back(which pushed the light forward) or press on the tab and gently pry on the side light.
Just as a note make sure you can see a split in the glass between the side light and the headlight(like a seam) so you know you do have a two piece light assembly. Give it a try and if you still have trouble let me know and I will guide you more and try to find some BMW instructions with pictures for you. Thank you!
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman