Permanent update and plug in?

Hello guys, im planning to do a permanent update regarding with a new Add-on. Im just wondering how is this possible to engage. Here are my questions:

• If the The main file will be not changed, but there is some .atl and burshset what i would like to expand and-or update then i have to upload again the whole package?
• How the buyers could knows if i made changes, updates? Are they get any notice from the Envato if the item what they bought before is changed?
• Is it possible to give or share the extra items for free, and place those on an independent site but put a link under the preview on the item change?

  I put a link here to understand what im talking about: http://www.youtube.com/watch?v=GpwTlPYK3xU Thank you for the answers, advices in advance!

- You must re-upload the full package, including the original files.

- Buyer will not get any notifications, just update your preview image saying that you’ve updated, and also leave a comment telling that you’ve updated on your item page.

- You can share the extras as a freebie, just put the link in your item description.

Thank you Elilsakov. The last info very good and promising. Im just sad a bit because of the first 2 because as it seems like the former buyers only will knows about the update if they gonna watch and check the actual item time by time.