Humaid.
This car has so much potential.. But if you are afraid of warranty then just don't upgrade at all.. Because what ever you do how small it is they will tell you that this caused the problem.. So Do what I do and just forget the warranty and do what ever you want to do with it.. If I have a Lumina SS these are the mods I would do personally.
1- Change it to manual gear.. ( AAT Garage in Sharjah can do the conversion )
2- Install a bad ass headers and exhaust ( Fox Exhaust )
3- Install a supercharger. Vortec ( AAT installation and you can order it your self )
4- Upgrade the brakes to either brembo or Stop tech
5- Buy new set of tires every week..