I would change the gasket as it's in a very critical area. The biggest difficulty with it is getting the surfaces clean of the old gasket. I used the spray gasket remover and a Dremel with a wire brush. However, if it's been changed recently, I'm betting it will peel right off.
The grommet is a back-up to the O-ring and it's likely damaged. If you follow the sequence I've mentioned, you will find it's easier than expected. The main thing to remember is to slide the grommet down last.
Push it down with a rag wrapped around it then clean with brake cleaner might help the grommet "grip" the tube and stay in place.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )