Changing a scratched glass

I scratched the glass of my watch. The LCD is usually working, but I hate seeing the scratch. I found some "glass" replacements on Aliexpress. I was willing to change it, but I couldn't find any reference to a "glass only replacement"; every piece of info I found seems to focus on a whole screen replacement.

Two questions: is it possible to change the glass only, and would it affect its water ressitance?