Aerial Grommet Replacement

[RickyBobby]

Had a look through some old posts and found a link to the young lad on YouTube doing the how to video but I'm still not clear.
My existing grommet has perished and fallen out of the hole in the wing so do I still need to go in via the boot and remove the whole aerial or can I just replace from the top using the screw method and some silicone lubricant?

 

[Davyhoogy]

I think I just popped mine out from above using a screwdriver carefully and slid the new one in. It might help to remove the aerial from inside, it would only take 30seconds its just 1 bolt