To remove old backups .... Launch iTunes on the Mac and go to iTunes>Preferences>Devices. All of your backups will appear in that window. Click on the backup that you want to delete and then click on Delete.
When you restore from a backup - you restore everything that is contained in that backup including all of the device settings, app data, Safari History - and everything that iTunes backs up.
However, restoring from a backup does NOT restore the iOS software. It is not a start from scratch type of thing. In your situation - You want to restore from a backup, not restore the iOS on the device....but remember that you are restoring everything that is in that backup - onto the iPad again.
How to backup and restore from a backup