Replacing spark plugs on any late model Volvo is not too difficult. You will need a Torx screw driver to remove the plastic cover on top of the engine. The plugs are sunk in deep wells in the center of the cylinder head. You will need an extension on your socket wrench. The plugs require a smaller socket than most spark plugs (16mm, if I remember correctly). A short piece of appropriately sized rubber hose is handy for starting the new plug into the head. Check to make sure you are not crossthreading the plugs before applying the wrench. Use of antisieze on the plug threads and dielectric silicone grease on the plug connector is a good idea. The cylinder head is aluminum alloy so torque is always important (25 Nm or 18 lbft according to Haynes manual).

Peter Bradley
2001 V70 T5
1969 1800S