I plan to format and reinstall. Is there anyway to find out how big all my updates were so I can calculate how much bandwidth I'm going to need when I update after reinstalling?
Windows will use what it has. If you allow automatic updates, BITS (Background Intelligent Transfer Service) downloads in the background so you may not even notice it. It has to work for folks with dial-up connections, so other that giving it all you can, calculations probably aren't necessary.
Most of the downloads are fairly small. SP1 came down in 4 parts and I believe the largest was 77 mb.
If you are running Windows 7 Ultimate, I would suggest you not allow the language downloads since those seem to be around 4-6 GB in size.
You can hide updates like Silverlight or some others and wait until later to download those, or you can choose to install Windows Updates only so some things will not be downloaded.
I would probably go to Windows Updates and select the option to check for updates but not download or install until you approved. Then at least you could pick which ones you wanted.