Computer showing Misfire Code

HI folks. I am new to the board, found this board when I was looking for info on my problem. Well here goes. My check engine light came on about a month ago on my'01 Cherokee Sport. The vehicle had been sitting at idle while I went in a store for approximately 30 minutes. When I came out the light was on and has not gone off since. So, yesterday I finally got it into the local dealership for a check. After 4 hours of waiting they told me the code the computer has stored is P0306, indicating a misfire in cylinder 6. The tech said that it is misfiring about once every 300 fires. Now, he told me that this is right near the acceptable range for misfires and I should not worry about it. He overrode the check engine light and reset it so that I didn't have to look at it, assuring me that it probably would not come back on again. Also, the tech said he switched the spark plugs in cyliders 6 and 3 and still saw the misfires in cylinder 6. SO, it's not the plugs. Anyway, needless to say the light came back on yesterday about 4 hours after I pulled out of the dealership. Again, the vehicle was sitting idling while I was talking to my accountant and when I got back in the light was on. So, does anyone have any idea what is causing this. My only thought is that it's the coil pack. The electrical stuff is out of warranty on my vehicle as it has hit 80,000 miles. So, I would like to avoid a costly trip back to the idiots at the dealership. ANybody have a solution or hints. Thanks a bunch. Sorry for the lengthy post.