Hi the only way to get to the back covers is remove the headlight assembly, remove silly trim panel over the light which is held on with a twist clip, remove the two screws that secure the unit, pull out light so you can remove wiring connector and remove the unit, the ballasts are attached to the rear covers which need to be unscrewed and pulled away from the connectors, then remove the covers and get going with the hair dryer, when reassembling coat the gaskets with silicon grease and put the thing back together.
Steve.