Go to this Dewalt DC988KA breakdown
http://www.toolsandmachinery.com/index.php?cPath=1_346_363_375&&page=2
and you will see item # 22 (brush box). It is a whole brush assembly and they will just clip into the motor. Grab a screwdriver and pry the old brush assembly out and replace with a new set item # 603754-01.
Don- www.toolsandmachinery.com, January 2009