If they can access the crack from the back, they can probably repair it. Again. hard to say not knowing the type of plastic, but the repairs I have seen involve making a "V" shaped depression on the back of the crack and "welding" with plastic. This should provide structural integrity anf prevent further deterioration/spreading of the crack. It's then a decision of whether to go further to finish and repaint the front side, or live with the crack in the paint.