Business accounts, yes.
If you are using FP1 with your personal account, you will either need to use FTP to transfer your files over after editing locally on your server, or consider upgrading. For personal accounts, the method used to make changes will change slightly. For domain accounts, the extensions were updated automatically. There will be no need to sign up again. If you are already using the FrontPage 98 client, your software will automatically detect the upgrade, and enable the missing features.