Is it permissible to complete the sale of audio tapes to a buyer who will use them in a church, and what should be done regarding that? And is it permissible to generally sell tapes, antennas, and satellite dishes?

It is not permissible to sell tapes to someone who will record on them materials related to the church and its doctrines, because that constitutes aiding in polytheism (shirk). If the seller knows that the buyer will use the sold item for this forbidden purpose, then it is forbidden for him to sell it to him, and he must annul the sale if he is able. If it is not possible to annul the sale, then the price is not lawful for the seller, and it should be spent on the general welfare of Muslims, because it is the price of a forbidden benefit.