I would personally choose to purchase a GPS system that is sold individually. This way I can mount it wherever I want and choose the GPS I want. Getting a factory installed GPS does not allow you these options.
They are equivalent, except the aftermarket systems can be removed easily.
The factory sensors can be installed into most wheels.
To install an aftermarket or work on the factory installed one, YES.
It was not a factory option. It can be added by aftermarket parts.
No the Volvo XC90 does not come with a GPS device standard but can be added through a Multimedia package for $2500 or a portable GPS can be added for $890
Portable GPS units work anywhere, in any car or handheld. A factory installed GPS unit generally cannot be moved to another car.
I think if you know what you are doing, then buying a store bought one would be fine. If you do not know how to then I'd suggest having one installed by the factory.
Have you installed an aftermarket radio or is the factory radio still installed? I had put in a aftermarket radio on my 04 Grand Prix and it does not keep date and time installed. That's because the factory radio holds that information for some reason I dont know hope that helps.
Only if it was installed aftermarket, they do not come with them from the factory.
Depends on the year, make and model of car, whether it is a factory installed or aftermarket sunroof, and what is wrong with it.
I do not know how much it would cost to have a factory sunroof installed by a dealer, but I expect it would be a lot more than a a respectable body shop would charge to install an aftermarket one
The factory installed alarms are normally better and more reliable that aftermarket type.