>any trick and tip what to do here? is it easier to put the grommet on the
>line and then push the grommet in with the line? any tools of help?

Spray rubber with silicon lube or similar.

Also, when tank is down you may want to replace the fuel level
sender...they are around $40, easy to replace now, a PITA if you have
to drop the tank again to do it in the future...