Yes it is correct. And yes you can follow action. Only thing you cannot do is adjust focus. For that you will need an external monitor IMO.
I would be happy to make a video for you showing you how LV works, but unfortunately I don’t think I will have the time — at least before the week-end. You may find something on this forum or over YT however.
Thanks again for your answer! Anyway I bought a 5d Mark III today, I've found quite an occasion! Around 10k shutter actuations, not even a small scratch, for 550€! Not bad at all! I'll receive it next tuesday and I can't wait to try it!
By the way this camera has a firmware version 1.2.1, should I upgrade it to some particular version before installing Magic Lantern? And why on Danne's repository there are two distinct builds?