This one I guess you mean?
Agree with
@Guinessisgoodforyou own view - minimum to make it safe and rideable.
This particular example is for sure rare and in good condition already. It doesn't look like it has had many miles put on it, and I would guess nothing is really broken. Obviously would need new rubber / plastics since they have perished with age. I would be inclined to only use a bike like this for "Sunday Best" as it were; I would pick something else (errrr ...... n+1) to have a daily rider. This MB is a bit too special.
The original paint and transfers would be best to keep intact - the French forums generally recommend to keep the patina (but that's France in a nutshell isn't it? Just look at other things .... ). If there would be a need to do a re-paint a top professional job is needed to keep the value. Full careful strip down and rebuild after cleaning up all parts would be enough for me. I've generally found that a lot of the parts can clean up really well. Some times the dirt and grime as actually protected parts.
One point I am struggling with though, many of these older bike were built with rustless spokes. Early stainless steel spokes didn't seem to be that good. The spokes themselves are usually incredibly thin single gauge. For me the wheels would be the only thing to fix which wasn't broken and it would help cleaning hubs and rims properly.