The ignition is a system. First you list the symptom, then you list the engine size. That's rather important when you're talking about what would appear to be an engine problem. There's four different engine sizes with three different types of ignition systems. Once your mechanic knows the symptom, he will do some diagnostic steps to determine what is wrong. If he is lucky enough to be told any relevant history leading up to the problem he might be able to save you some money by not wasting time repeating some tests. The cost will be the shop's hourly rate, which we don't know, times the number of hours it takes to determine the cause of the problem, plus the time to replace the parts, which we don't know, plus the cost of the parts, which we don't know. Does your mechanic use parts from the dealer to insure a quality repair, or does he order high-quality aftermarket parts from a local auto parts store to save you money?
There's way too many variables when we know the symptom. With the information you provided, you can get a good idea of the cost with a dart board.