Depends on age of the face, material used and what kind and how many layouts have been on it before.
If it's polycarbonate, there will be an increasing amount of yellowing where there was no vinyl. If it's high-impact acrylic, there will be no yellowing, but they are much, much easier to break.
If translucent vinyl was used and it hasn't weathered too badly, it's easy to take off with very little adhesive left to clean. If the vinyl has deteriorated badly or they used cheap calandered vinyl, better to throw the face out and start new.