00 GA SE ABS, BRAKE, TRAC Lights

i have a 2000 grand am se with the 4 cylinder engine,
like many others i have been experiencing intermittent low trac, trac off, abs, and service vehicle soon lights (notice it mostly happens during or following heavy snow and slushy days)
i took it to the dealer and they said that the sensor in the passenger side front wheel is bad and therefore need to replace the hub since it is a solid unit
they also said that my brake sensor is bad and that i require that to be replaced too. ive looked in my manuals and only reference to brake sensor im seeing is the brake light sensor on the upper end of brake pedal. is there another sensor called just the brake sensor somewhere and if so where is it and how do i test it?
the dealer wants $350 for the hub work and $50 to replace the sensor, sounds little expensive.
any information helping out is appreciated.

That sensor is part of the hub assembly, so the entire hub unit will need to be replaced. That sounds like a dealer-accurate price also. They always rip you off. If you go buy that hub assembly yourself, it will be 150-200 dollars (if you can do it yourself). At least buy it, and then have a shop do it. Just not a dealer. They will always rip you off.

the dealer is trying to make it sound like it is one sensor in the assembly which requires the whole hub to be replaced which is the 350 parts/labor and then he is charging me a seperate 50 to replace the brake sensor that your telling me is also part of the hub ???

Yes. So they're feeding you bullshit apparently. The sensor comes with the hub unit.

well unless they're talking about the opposite end of the sensor (the car based sensor end) - Im not sure then.