rear brake light comes on

my rear brake light on my 2000 buick regal comes on. it started a few weeks ago. i had new brakes installed but the light still stays on. someone said there is a line on each wheel that goes to a sensor? if so, how do i go about taking the lines loose and cleaning them? how hard is it to put new sensors on? how much are they? and where do i get them? send e-mail if you will. purecty@yahoo.com ty. kindly

Your wording is not very clear. Are you talking about the red brake warning light, the abs light, or the actual tail lamps are on when you're not on the brakes?