If you cannot afford a backup warning system, purchase wide angle mirrors that are inexpensive but allow you to have a better view behind your vehicle.
Dealers of car parts and accessories often have web sites that allow consumers to search by make and model of their vehicle. There are generally online catalogues which can be browsed to search for special items such as tools that may be needed to install parts.
Repair manuals for automobiles can often be purchased over the Internet.
Keep in mind that auto parts and accessories are more expensive for foreign cars.