RB is a dead easy colour to spray and match to thats a bonus. Full strip & repaint is required if you want to use your exisiting bonnet, this will be costly stime wise. Personally id be looking for a used bonnet or a new bonnet and having that sprayed, will save the stripping process.
New bonnets are pretty cheap from Renault, depends if your existing bonnet is dent free (unlikely!)......if you strip it, it will have to be really well stripped ATLEAST to the sealer else it might come back to haunt you in your new finish.