I've answered a lot of stuff about the FAMAS in other threads if you bother searching: in a nutshell, it's NOT a good beginner gun, so I'd recommend you avoid it for now. Doubly so if you plan on doing mods.
The G36, by contrast, has a lot of commonly available parts and upgrades, and it's modular design makes it easy to customize (not to mention you have several different brands and models to choose from right off the bat); various lengths, carry handles/optics, AG36 grenade launcher, etc.
And off-topicly, the Légion Étrangère (French Foreign Legion) are indeed some of thoughest guys around. However, as the name implies, except for the REMFs it's made up almost exclusively of
foreigners (i.e., not French). Also interesting, when joining the FFL, you swear allegiance to the Legion, not France.
Great info on the Legion:
http://www.foreignlegionlife.com/