> Is there a way to run an update without it
> downloading everything again???? Thanks.

It doesn't download everything again, it asks the server has this file
changed. Very fast (~5 files per second.)
Only dynamic html files need to be redownloaded.
If the website was rebuilt (and the webmaster didn't preserve timestamps
properly) then it gets redownloaded.
If you Canceled a mirror, as opposed to pauseing, then everything after that
point is lost and gets redownload.