Complex sentence: The chalice and paten would need to be consecrated with the chrism again if they are re-gilded, and this ritual may only be performed by a Bishop or a priest with the faculties to do so.
Split into simpler sentences: The chalice and paten would need to be consecrated with the chrism again if they were re-gilded. This ritual could only be performed by a Bishop or a priest with the faculties to do so.