i am not a proffesional magia(checker) but as a sofer i would assume that if the mezuzah was good in the first place and you trust whoever checked it when it was first bought then theoretically someone with basic yeshiva knowledge should be able to tell if something got damaged and then show it to a rav.The big problem i see with it is how are you going to properly rewrap the mezuzah and return it safely without a-damaging it and b-leaving it exposed to moisture.thats where you are going to need a professional.while its really no big deal for someone who learned how to do it,once you bring it to someone you"ll probably get him to check it as well