3
Since upgrading with such a big leap is always tricky, I suggest the following procedure:
1. make a backup of all the files and the database
2. setup a test site using the backup files, so you have an identical copy of your site
3. download and unpack the latest stable version, not the upgrade, but the full version
4. overwrite all your files with the new version
5. run the installer by going to your testsite's root url. The installer has a built in updater for 1.x sites. It'll detect the tables in the database (if you fill in the correct information during setup), and upgrade these to the 2.0.x structure.
6. Test if it works
Herko