Engine Performance problem
1999 Ford Expedition V8 Four Wheel Drive Automatic 80,000 miles

Hi:
My 1999 expedition has been sitting for about a year. It has been used on occation; however, because we can't afford gas prices, the vehicle sits 99% of the time. After sitting for several months, I started it to use it. It now has a miss under a load at a lower RPM. Do you think it is a coil or should I just replace the plugs? Also, I was told 5.4L is very hard to replace plugs on. Do you have any recommendations?

Thanks,
Joe