I had leaking sunroofs on my Espaces and very carefully cleaning the edge of the glass and the rubber seal then applying a light coat of slicone spray did the trick. I live near the sea and wind drives sand everywhere. Your leak may be due to some other reason but it might be worth a try.
Cheers, Andy
Just seal it up with clear silicone - who needs a sunroof at this time of year ? Worry about it when summer comes around and by that time you may have found a cheaper solution than refitting the whole unit. Leak can often be caused by blocked drain tubes - check this out.