If I use a trial Xbox Live pack, will it update my MS Dashboard to the latest? The reason I am asking is I think I might have stuffed something up in it. It seems to work ok, but I want to make sure its complete.

I dont think you have to have a trial pack to get the new dashboard. All you have to do is sign in to a newer game and if you dont already have the newest dashboard then it will download it for you automatically.