[RBS] Question on Car Warranty

[Ramat Beit shemesh]

Hello,

Can anyone tell me how I find out if I MUST fix something at a car
dealer where I got my car. They stated to my wife if I fix something
exterior (wheel protector and dent in bumper) at my mechanic my
warranty will be voided. Most likely they will be more expensive than
my mechanic which is why I am leaning away from the dealer.

How do I ensure I am protected.

Thank you,

Dov