1999, 140,0000 miles--Land Cruiser--misfire on cylinder #6

Garage reminded me this happened two years ago with another cylinder. Now, it’s cylinder #6. (garage said they replaced a plug & a coil. What’s a coil? Spark plug wire?)

Is this a hard, expensive repair? I think I want to fix it and immediately sell the car. Sadly, I think I have to part with it as I can’t afford the maintenance and I can manage share my husband’s car. Anyone know what it’s worth?1999, 140,000 mi