I am planning for a long road trip (about 17 hours of drive). Is it safe for my one-year old baby to sleep in her car seat for such long hours? How often should I stop to take a rest and how long should each rest be before continuing?
The bad news is your baby is going to make you stop whether you want to or not. The good news is that makes it so you don't really have to guess how long is too long. You know how long you go between diaper changes and feedings now. Plan to stop at those intervals at the very least, then double it to get a probable worst case.
As for how long you should stop, your baby will cue you on that too. Whenever you can put her back in the car seat without her immediately starting screaming. We've had babies that you could just change a diaper and put them straight back in, and we've had babies that require 20 minutes of rocking before agreeing to go back.
Our rule of thumb is that traveling with children adds 50% to the time. That means if google maps says 17 hours, we plan 26. Also, our family can't take much more than 12 hours without stopping for the night, but we know families who just take turns sleeping while driving straight through and they do okay.