Spark plug gap width - as you look at the spark plug, obviously, there are two ends. One end will screw into the spark plug well - be very sure you don't cross thread it. On the plugs in front, you should be able to screw these in by hand at a minimum. The ones in the back, you can still screw them in by hand, you'll just have to contort yourself a bit more.
As you hold the plug, you'll notice that there is a little shaft that is bent over at about 90 degrees. This is where the gap is measured. If you buy your plugs at O'Reilly's, ask them to gap them for you and watch how they do it. To measure the gap yourself, you'll have to buy or borrow a filler gauge. Any autoparts store will have these on the counter at ridiculous mark-ups, selling them for a buck. They sell them this cheap because they know that everyone loses these and will have to buy about five more before they die. If you have the circular type of gauge, you'll notice that the gauge gets fatter as you rotate it. (Or thinner depending on which way you rotate it) Slide in the gauge at the thin end, spin it around until it stops wanting to slide and assess the gap. If the gap is too large, you'll want to take your thumb and press down on the bent arm. Don't worry, unless your green with a temper, you're not likely to press it down too far the first time. If the gap is too small, use the aforementioned gauge and gently press up against the bent arm. Then reassess.
This forum is full of guys that have over-torqued or under-torqued and had bad results. The ones that didn't use a torque wrench and had no hassles won't need to post here for help. You can a)recall how much effort it took for you to remove the old plug; try to use the same effort to reinstall. Or you can get a torque wrench. They come in many different types-- I'd get the sales man to show you how it works. Each wrench has a range, and they may need to be recalibrated from time to time. Myself, if it's something that MUST (as opposed to should) have a torque wrench, I consider it a complex procedure and let the trained professionals have a go at it.
I recommend you get a torque wrench;at your novice level, you may as well learn how to do things the right way.
In the chiltons manual, the pictures are pretty good. Be advised that there are some errors in it. I suppose if you do a search for Chilton's and errors you'll find them.
Good luck.
