Clear the codes, run it again and if the MIL comes on see what the codes are. If it's the same then it identifies the cylinder and a misfire. By far the most likely things as said are either plugs (age and gaps) or the coil (or both?).
I don't trust most places giving that sort of diagnosis. Of course they might be correct, but odds are it's something much simpler.
Are you able to change plugs and/or coils yourself? The coil is simply unplug and plug in a new one. Not sure of your engine, but usually the connector is directly on the top of the coil body, and they are typically held in place by one bolt. Others will advise.
If you can do it, mark the one with the fault code (tape/felt pen etc) and swap it to another cylinder. Clear codes and try again. If the fault moves with the coil then bingo. If it doesn't then at least it's ruled out (probably).