If I install a new ROM does that erase all my installed apps and dat? If I have a rooted (Razr M in this case) and want to install an updated ROM (e.g., to upgrade to a new 'Droid OS version) will I need to reinstall my apps and restore my data?
Unless you wipe all your data before the update, you do not need to Reinstall applications or Restore application data. But when flashing a completely different new ROM, it's recommended to do a full wipe before proceed. Further more, If you are planing to do a full wipe you can use a application like My Backup Pro or Titanium Backup to back up all your applications and data.