hey guys...i have a 2002 trailblazer i have no brake lights...the fourways turn and marker lights work fine..brake light switch? is it hard to change? also have a problem with oil pressure,when at idle the press drops to 0 while driving its fine....there is no noise from the engine when this happens and it drops like someone turned off a switch sending unit or sensor? where is it and is it hard to change?....thanks

I would check for current in the stoplite sockets to start with. I would also get a test gage on the op senser port to see if the press. is acually low.