Brian,
Curiosity brought me back to your dilemna. I didn't realize that your winters were so cold. Volvo has definite recommendations for oil viscosity for low temperatures which may help your problem. Check your owners manual.
To answer your other question, the easiest place to open up the intake system is at the connection between the turbocharger piping and the intake manifold. If you're standing in front of the car, there is a large black metal pipe that runs from the turbocharger next to the fire wall straight towards the front of the car between the airbox and the valve cover. At the transition from metal pipe to rubber hose there is a clamp you can loosen and separate the pipes.
If you get the car running again, I think the tailpipe test may be the easiest.
If you floor it and look in the rear view mirror (briefly, of course, things can get out of hand quickly in that car), and see any type of grey smoke the turbo is probably damaged. I'm curious if the error code has reappeared, and if the plugs are starting to degrade again.

Mark