I've never changed a bulb on a Grand Scenic but just to put your mind at rest if you ever need to take the front end off it is a lot simpler than you would think. On a Megane CC there are a couple of screws under each wheel arch 4 across the bottom and then it's just a case of using a philips screwdriver to release the plastic clips across the top under the bonnet. The fastest I've done it in was 15 mins.
However I came across this on another forum that I think will be just the ticket for you.
Well 2 hours today finally got my headlight bulb changed in the Scenic. In case it happens to you, here is how to do it (that is if you don't have a friendly dealer who will do it for nothing!
Halfords bulb to use is No 477, think it was £8.99, the dealer wanted over double that. The bulb is not shown in the wee guide book at the bulbs, had to ask at the parts desk.
Now this was passenger side bulb so firstly, unscrew the bolts on top of the battery cover and lift out of place. It is also held onto the front bulkhead with some sort of poppet which I couldn't free up so just twisted the cover out of the way.
Slipping your hand down as close to the battery as you can as opposed to the wingside) you will find a large rubber cover. Remove this simply by peeling away at the edges. Under that you will find the rear of the bulb. Now handbook says try and disconnect socket at rear of bulb, but a quarter turn in the combined unit will remove it all from the light. Then prise the bulb and the holder apart (I had to use a screwdriver for leverage).
Put new bulb on and clamp the socket back onto the bulb. Now switch your lights on to make sure bulb is working. On the bulb, there is a "prong". Now on the rear of the headlight there are protruding "screws" at the 3 o'clock and 9 o'clock position. You want to slip the bulb into the hole, making sure the prong is approx 8 O'clock, and then turn slightly clockwise and this will lock it into position.
Replace rubber cover, replace battery cover and tighten screws and hey presto, all done!
Now between SWMBO and myself, I reckon we have well into double figures of cuts and scrapes, but job done!
Incidentally, the drivers side looks a lot easier, just unclip the washer bottle and move out of way to have (almost) full access to the bulb.
Hope this is of help