“If your brother sins [against you], go and tell him his fault between you and him alone. If he listens to you, you have won over your brother. If he does not listen, take one or two others along with you, so that ‘every fact may be established on the testimony of two or three witnesses.’ If he refuses to listen to them, tell the church. If he refuses to listen even to the church, then treat him as you would a Gentile or a tax collector. Amen, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven. Again, [amen,] I say to you, if two of you agree on earth about anything for which they are to pray, it shall be granted to them by my heavenly Father. For where two or three are gathered together in my name, there am I in the midst of them.” Matt. 18:15-20
Talk to the priest directly before you drag anyone else into it. You cannot know the entire situation without doing so, and you do not want to be guilty of rash judgement. Besides, he deserves that you discuss any wrongs he has committed against you with him directly before assembling any consensus against him. That is the way the Lord directed you to do it.
Approach him respectfully, because the Lord has put him in authority over you. Besides, he has faculties in your diocese because the bishop is satisfied that he knows and has been keeping up on the liturgical rules. Show respect to his superior knowledge, as well, then. Speak to him as you would want a student to speak to their professor, as a son or daughter to a father, for he has been placed as a father over you.
If leave him still convinced that he is in the wrong, and the question is of sufficient gravity, you can ask the vicar of clergy for your diocese about the question. If you do not leave him convinced that the matter is settled, you can ask the bishop directly. If the bishop will not hear you or cannot convince you, or if they do not listen to a complaint from a single person, then you can consult with fellow parishioners, in order to assemble the required quorum needed in order for a question to be taken seriously. Again: do not forget the position the Lord has given them, and approach them in a humble fashion, ready to learn from them. Do not leave yourself in a postion of being “invincibly ignorant” (so to speak) of the true liturgical requirements, the authority over which God has given to the successors of the Apostles.
If it is a question of a truly serious nature and there is no redress at the diocesan level, you can appeal to Rome directly. The division of the curia to contact is the Congregation for Divine Worship and the Discipline of the Sacraments. If Rome won’t hear you, then you have no recourse but to commend the matter to Heaven, content in knowing that you have been invincibly ignorant of the liturgy in good faith or that you have done your duty.
Do all of this so that your conscience may be clear of the charge of having been a capital pain to your superiors when you were in the wrong after all was said in done. Be as persistent as conscience requires, but always be circumspect about the humility with which you persist. Pray to the Doctors of the Church to be your particular guides and intercessors, particularly St. Teresa of Avila and St. Catherine of Sienna, as neither were priests and both had to endure some persecution for her efforts at reform.
I think that if the priest apparently will not listen to you when you approach him, and yet does not repeat the fault in the future, let it go. Provided that he repents of the problem, the less you act as if he is any need of oversight from you or any others of those over whom he has oversight, the better.