1. Backup your files and database
2. Read the upgrading instructions and changedfiles
3. Use a file compare tool to get you hacks into the new version
4. Close your forum
5. Upload the new files and run the altertable scripts if necessary
6. Test if everything works
7. Reopen the forum
If you use many hacks and/or you are going to make a major upgrading. I'd recommend to setup a test board, so that you can make sure, that everything works as indented.
