This job is a total PITA, perhaps one of the worst jobs on a volvo from a general maintenance perspective. First off most mechanics tighten the nuts with an air gun, so getting them to unscrew is a nightmare. Second, unless you have a lift to get access to the unit from a standing position it can be a horrible experience getting leverage on the unit without totally removing the filter/pump from the vehicle.

I would suggest you find an indy guy and just pay him to do it. The job shouldn't take more than a half hour or so, and the cost for the labor is more than worth the avoidance of the hastle.

good luck,
rt

p.s. the washers mentioned in the other post are the "crush washers" used all over your brick. you can get them at any volvo dealer.