Can the window that opens stating that an update is available also tell when the update has been applied (i.e. curse client has installed the addon successfully)?

Also, I am getting multiple messages for each update... for example, if Deadly Boss Mod has an update, I get 4 message windows.

You posted on the wrong forum. This is Vanguard forum. Curse Client no longer support Vanguard. :(

You probably wanted to post on WoW forums.