You don't know what the will says yet. On what grounds do you anticipate challenging it? If anyone, including an executor, has removed or disposed of property beyond the terms of the will , they are personally liable to the estate.Beyond that, you will be challenging the will. You have to show mental incapacity,that the deceased didn't know the nature of the will (that it was a will) or that they didn't appreciate some material part of it, or that there was undue influence on them, suborning their true, free wishes, or forgery or fraud or that the will is not valid as being not in proper form. None is easy to establish, though undue influence (the usual favourite) or non-appreciation are easier.