windscreen rubber

Hiya, I have just bought a 07 laguna dynamique 2.0 dc.

I dont know how, but did not notice that the rubber seal on the drivers side of the windscreen was missing.

Question is, is this going to cause a water leaqk, do these come in one compleate unit or in sections,?

Does anyone know where i can get one.?

Is it a D.I.Y or operator job?

Thanks in advance

BB