Thank you all for your comments (PratoN, me2000, suss6052) !
Here is a photo of the worksheet with everything they've done to the car.
Sorry for the low quality (and yes, it is in French), but iPad 2 is really what I had with me to snap a picture of it.
I have an advice to anyone who feels that something is fishy with their transmission : Keep going to the dealer and if one says "It is normal behavior !", well, don't stop there ! Look for another one and get the car to him.
me2000, I don't think the fluid got into the clutch. I checked on the net the different parts, but I am a noob when it comes to engines and it seems to me they were changing bolts and something like this.
P.S. I have one thing to say though : I still hear from time to time the "grinding" noise on my tranny (when changing from 1st to 2nd), but I think it is not a real problem. I can reproduce the grinding noise when pressing very light on the throtle from a full stop. If I press a little bit harder, the grinding noise is not there. If the noise will become too important, I will take it back again. At least, now I know WHERE to get my car to be fixed.
P.P.S. My car idles now at 630-650 as it was before. No more the feeling that the engine is "loaded". And finally, I saw the "mpg" comming up to where they were before, from a 8.9 l/100km (29.4mpg) to a 6.9 l/100km (34.9 mpg) on a short trip on the highway (20 km -vdriving it at a speed of 116 km/h = 72 mph).