You won't have to reflash the N900 using Flasher or PC Suite software, It will be an incremental updates you'll insall via the App Manager. The usual routine is that you will get notifiction when it's available. When you go to installed it it will say that you should make a Backup of your device, before proceeding. You should follow that advice. When you proceed, the N900 will start performing the update which will take a bit of time.After it's done, the N900 will reboot (usually). And then.. well that's all.