Restoring front and rear valances under bumpers?

Just wanted to know how hard it is to do the bodywork yourself on the valances, theres quite a alrge area of surface ruse on both, more worryingly the rear, but all seems to be pretty sound? i dont kno whethe to grind away the rust and see how deep it goes, then attempt to fillers smooth and spray? or to get it done by an expert as the car is currently battleship blue/grey so may get a respray? or keep the original colour? need sum help peeps!