Standard disclaimer: Working on your car can be dangerous, etc. That said, this is one of the easiest fixes you can do yourself. If you do it wrong, your car won't start or if it does, it will run very poorly, so there is little chance of taking your Volvo out on the road in an unsafe manner.
5/8" Spark Plug socket
ratchet wrench and extension
T30 Torx driver or socket
Optional: feeler gauges
4 spark plugs (I used NGK BKR6E)
2 coils (volvo part number 1275602)
spark plug wire set (volvo part number 1275603)
Step 1: Open the Hood; Remove Plastic Cover
Open the hood, locate the plastic cover that hides the coils and wires. Carefully remove the 6 bolts that hold it in place. You will need to use the Torx T30 tool to loosen these bolts. The cover is also held in place by two catches on the left edge, front and back. See photo for clarification.
Step 2: Remove the Wires From Cylinders 1 and 2
Step 3: Remove the Old Coils
Step 4: Check the Gap on the Spark Plugs
Insert the new coils into the far right wells, making sure to align the hole for the securing bolt. use the 10mm socket to secure the coil hold bolt. Attach the control wires making sure they are secured with the clip.
Install the plug wires into the left wells. Make sure the wire labeled "1" is on the far left (as you face the car - this is the passenger side of a Left-Hand Drive model). Route the wires as seen in the photo - wire "1" is attached to the coil on the other end of the engine, which is cylinder #4. Of course this means that the #2 wire is connected to the closer coil, over cylinder #3.
Step 6: Reinstall the Plastic Cover, Start the Engine. Check Other Vital Fluids.
Once it is all secure, you should start the car and ensure it runs smoothly.
Turn the engine off.
While the hood is up, you should check the other vital fluids: Oil level, windshield washer fluid, power steering fluid, radiator coolant and brake reservoir.
Close the hood and go for a test drive to make sure all is well. In my case, the hesitation was gone, and driving was much improved.