Looks like I was making a mountain out of a molehill. My glow plug kit hasn't arrived yet but I got impatient and took a stab at removing the glow plugs. The clips came off easily with a narrow pair of needle-nosed pliers and the first glow plug I tried (#2 seemed to have the best access) came out smoothly. The next one was giving some resistance so I sprayed some PB Blaster and warmed up the engine to 170º. Without waiting for the engine to cool, I removed the remaining four glow plugs without exceeding more than about 15 Nm of torque (guessing).
Ironically, it looks like getting at the bolts that hold down the control module might be tougher than removing the glow plugs.