It should not be a problem Walleyerich as many have updated their software this way. Just make sure and force it into the Simulator mode when you reset the menus to the factory settings or it will not take – which can potentially cause a problem.
Forced Simulator: power the unit on and while it is showing the start up title screen (will show something like: “Humminbird 798c SI”, you will need to press the MENU button. This should bring up some menu options. Select the one that says “Simulator” and let it time out. This is the forced Simulator mode (because you had to force it into this mode) and it will remember all menu settings like the unit does while in the Normal operation mode. If you were to just have the power connected and powered the unit on it would automatically go into the Point Of Sale Simulator mode which does not remember menu settings and will automatically reset itself after two minutes of not pressing a button.