You might want to start looking at stuff like this:
http://www.ravelco.com/magnusonmossact.htm. I'm sure the actual text of the law is available on the internet, too. What it boils down to is this--in the US, dealers cannot deny warranty service due to aftermarket
mod's, unless THEY can PROVE that the
mod's themselves caused the need for repairs. $1000 for a brake job is rediculous. Of course, I usually do my own work. Still 4 rotors + brake pads is probably <$500 and it'll take around 1 hour to change it all out. Also, you probably don't really need new rotors.