Do you know anyone from the church? If you do, ask them what would be a good way to make the proposal. If not, contact the church office and inform them that you are interested in this project and ask what would be the best way to proceed.
Most Presbyterian churches are actually quite organized, with admin policies and committees etc. So there is probably a formal procedure that you'll have to go through involving a memorandum of understanding which will describe responsibilities and obligations of each party, insurances, indemnifications, etc.
Most churches are very concerned with limiting their liability, so it's unlikely that they would allow you to reside on the land. But there is a LOT of precedent of
churches hosting community gardens on their lands, so you might see succes with that tactic.