Very necessary.
Without, you may get lucky or you may fry the output transistors of the radio
x2. you don't tune it just for "clarity" or "reach." You tune it to ensure you don't fry your radio. Back before I knew better, I fried a CB from not tuning an antenna. If you're keying the mic, make sure its tuned. Its not hard to tune at all.
I've run 6 different antennas in the past. I'll never own a fiberglass one again. For a noob who just wants to plug and play, a lil wil magnet mount is your beat bet once you tune it.
Trokita, in order for your swr readings to be low, you're going to have to make sure your bed, bed rack, and mount are all grounded. That means no paint between mounting surfaces. Test continuity with your multimeter.
With a magnet mount, you throw it on and it's grounded. Tune it and you're done. Plus they're whip antennas which last a lot longer. Also keep in mind how much of your antenna is sticking up above your truck. You may have a sweet antenna that mounts on the back of your bed, but if it doesn't stick higher than the truck, you'll have limited range. Center of the roof is one of the best spots to mount one, followed by the center of your hood.