Yes, send one, with a little handwritten note expressing how pleased you are that he has agreed to officiate. But as implied above, don’t enclose an RSVP, and only enclose directions if the priest will need them.
If the RSVP asks about dinner preferences, ask the officiant directly. Be certain he knows he is being invited to a special place of honor at the reception. In our neck of the woods, he is customarily seated with the parents, unless other members of the wedding party are particular friends–as when a priest who is a brother to the bride is seated with his brothers and their cousins or school friends.
Sending an invitation is a nice touch, but not obligatory. If it is too late, and you haven’t, I don’t think he will take offense. What is obligatory is some sort of a stipend, preferably something that reflects the overall extravagance of your event. (Read: Don’t spend a ton on flowers and baubles for the flowergirl and then get cheap when expressing your appreciation the priest.)