When you purchase a new lock cylinder, it should come with neshoulw tumblers for keying to match your existing key. When you remove the old one, take a small screwdriver and pry out the old tumblers and lay them out in order front to back. Each tumbler has a number stamped on it, match those numbers up with the new tumblers and insert them into the new cylinder in the correct order. The new kit should have detailed instructions with pics. Mine did and it came from Advance Auto. There is no need for a locksmith or dealer either.