Micra K12 (07) Interior Damp Help

My Micra rear bench is soaking after sitting parked in the rain for days. There appears to be drips and condensation build up in the High Level rear brake light as well. Has anybody else experienced this? Appears to be a line of black silicon along the top of the tailgate glass which is gone at the passenger side.

Is the tailgate glass meant to be sealed like this? I will post a picture shortly (its raining at the moment picture wouldn't be that clear).

How easy is it to remove the rear glass and reseal and refit?

Many thanks