I feel your pain!! When the same thing happened to me, others suggested using a 17mm open-end wrench to pry off the boots. That didn't work; in fact, this resulted in a broken spark plug -- my first and only in 15 years of doing auto maintenance. Finally, after much more research, I used a SnapOn Spark Plug Boot Removal Tool (it's actually labeled Blue Point), part number SBP-3 (I think it was about $25 from SnapOn's website). However, what really made the job much, much easier, was using that boot puller in combination with a long-handled curved-nose needlenose pliers I had. I would grab the boot with the Boot Tool, and then use the curved pliers resting on the engine block to pivot the Boot Tool away from the engine (like a lever). Unfortunately, I only discovered this trick about half-way thru the job, after much sweating and swearing using the Spark Plug Boot Removal Tool on it's own.

Regards,
Steve
'98 E320 Wagon