To change notification settings:
Go into the regular mail app (not gmail) Hit Menu button -> then go to settings and it should be in there (I don't know for sure, because my email app isn't configured at all, I only have my gmail app configured)
To change the bottom dock to display gmail app icon instead of email.
From home screen: Go to
1. Applications
2. Hit Menu
3. Select View Type
4. Select "Customizable Grid"
5. Hit Menu again.
6. Hit Edit (at this point you will see all icons will get box outlines around them indicating you're in edit mode.)
7. Press and hold gmail app icon and once it becomes movable (after a second of holding it) drag it between phone and email icons in the bottom bar.
That will throw the email icon into the app list and put gmail icon in the bottom bar.
8. Hit back button
If you want to change your app view back to alphabetical, repeat steps 2-4 but select "alphabetical list"
Hope this helps.