Complex sentence: When the preacher gives them a chance to read the vows, Vince begins to read the vows she wrote for him, but tears them up and speaks from the heart instead which culminates in him telling her he really does love her.
Split into simpler sentences: When the preacher gives them a chance to read the vows, Vince begins to read the vows she wrote for him, but tears them up and speaks from the heart instead. This culminates in him telling her he really does love her.