This must be very frustrating. Unfortunately, parish priests in any country usually rank family history queries a lot lower than all their usual duties, dealing with parishioners and parish organizations, religious services etc. They are all likely to be busy people.
Was your letter in English or Polish ? Could that be part of the problem ? Sometimes an offer to make some sort of contribution to church funds or a parish charity may encourage somebody to get out the old registers. The Christmas/New Year period is possibly not the best time of year to get someone to do this research for you. I would routinely enclose a self-addressed envelope for a query of this sort and make it clear you don't want to leave the parish out of pocket. It is always possible that the parish priest is ill, so whoever is standing in for him is simply not inclined to deal with anything like this.
Can you ask the priest who offered you advice for help contacting the parish ?
