*Going back to original topic, since I know the poster kinda*
No matter what you do, depending on the amount of mods that have been made and your skill level at navigating them, updating to 2.0 properly will take time. With that in mind, try to follow this:
1. Keep your production shard online running 1.0.
2. All your upgrading should take place on an offline copy of your server, so your players can continue to play.
3. Go through every file in every folder and find any changes that have been made. Apply those changes as best you can to the new RunUO 2.0 files.
- This can get complicated if you or your staff haven't been properly commenting changes and noting changed stock files. If this is the case, you should either stick with 1.0 or restart your shard on RunUO 2.0.
4. Don't be afraid of compile errors, they are there to direct you to the places that need changes. Quite often, a compile error will alert you to a few changes you forgot about.
5. There are some notable changes to the RunUO distro that will make custom commands, context menus, and regions not work properly. This will take some research, and I have no doubt all questions concerning these changes will be asked and answered on these forums.
Upgrading will not be fun. It will take time. You may get headaches. If you stay the course and get it working, you will have had a valuable learning experience and will have a RunUO with many new and exciting features.
~Addition
And it has been said to remember that this is a only a release canidate =) I'd follow that suggestion, to wait until the final.