filling it in permanently is easy as.
I did it to a car of mine i resprayed a while ago. i am however a spraypainter.
But yes as it was sugested above the easiest way to do it would be fibreglass, or more specificly fibreglass reinforced filler. which is what i did.
the process is just tap the edges of the hole in i bit with a hammer basicly so the area around the hole is slightly concave, like the hole is in the middle of a dint. This is done to give the filler strength to cover the hole. Otherwise it would only be covering the actual hole so the filler would just fall thru. then put a piece of tape or tomething on the back of the hole, to make it possible to wipe in the filler into the "dint" without it falling thru untill it has dried. then wipe it in, rub back, fill pinholes etc with finer filler, rub smooth then prime rub smooth again, then paint.
It is a fairly easy thing to do. All the stuff u need cold easily be bought from supercheap. so you could save a bit of money and do it yourself if ur keen then get the pro's to put on the paint.