Obviously you'd have to dismantle the camera to get at it.
And it's likely you'd break it trying to remove it and take away the old sealant.
If so - a replacement or two is readily available if you do an eBay search for "watch glass flat" after you've measured the diameter.
And you'll need some epoxy resin or other strong glue for the re-seal.
And keep your fingers off the lens ...
So I figured out there is 2 tiny screws in the top of the camera housing that hold the black plastic face on. Then under the face are 4 screws to remove the front sensor housing from the main body. Looks quite corroded inside the front. And yes I cracked the lense cover so I'll be drying it out and getting a new cover. Thanks for your help
Fiddly, but quite do-able.