I would check with a Volvo dealer and buy the service manual for it.
This is a good idea for all of us, though Volvo makes it hard. Most shop manuals are in the $50 range. Volvo publishes the manual as sections at about $20-30 each. I've got:
1. Intake, exhaust, and cooling systems
2. Fuel and lubrication systems
3. Engine body
...and I think there's another 4-5 manuals I could have bought.
Still, it's worth it. Instead of trying to figure out how to get at that danged nut, the shop manual will take you through the correct steps so that you may not have to remove it after all!