[quote name='swetooth9']is the tuning complicated? i love cars, but no very little about the technical stuff like tuning gear ratios, etc...[/QUOTE]
It can be. You can get into the details of it all, but the actual buying of upgrades is really quite user-friendly.
There are bars and graphs that show you exactly what your improving from the basic stats of your car (Speed, Acceleration, Braking, Cornering, and Rarity). There's also a real-time indicator of how the parts are going to affect the vehicle's class.
You will have to work on some of the cars to get golds in the races, but not to the extent of raising ride height or stiffening the suspension.
It's as simple as, "I need more speed and better handling." You flip through the available parts and see how the car's ratings are affected.