To make it easier to remove the plug boots the next time, use a Q-tip to spread a little dielectric grease inside the rubber area of each boot. Works like a charm. Haven't had a boot stick for many years. Yes, a little twist of the boot before pulling up is the best procedure to break it free if stuck.

You may also buy a 5mm 3/8" drive socket. That, along with a short extension and a 6" drive did the job easily for me. Lots of creative methods employed by folks, though.

Good silicone rubber wires should last for a long time as the silicone resists heat and drying and cracking. Many folks leave the cap, rotor and wires on an engine for long periods of years and miles. This is not really a good idea as these parts deteriorate with age as they are subjected to the duty cycle extremes.

There is another plug type you can use in many of the Merc engines which call for non-resistor plugs. Nology is a silver electrode plug used for racing applications. Silver is an even better conductor than copper. The Nology plugs cover a slightly wider heat range, also. I have them in my '77 230, '90 300E 2.6 and have used them in several cycles. A little pricey but long lasting and with good performance.

http://www.nology.com/