Spent 1 1/2 hour in a complete darkness (with small flash light!) and freezing temperature to replace the sparkplugs today. Type of plugs I got are Denso Iridium Power plugs (IK22) that are one step colder than stock plugs.
****warning**** replacing plugs on boxer engine is very different from Honda engine, which takes only 15 min to do. Be prepared to spend at least 45-60 min to replace them if you have never replaced plugs on Subaru vehicle before.
1. Starting from the driver side, remove the washer bottle and the battery to gain good access to the "coil on plug"
2. There is one 12mm bolt you need to "break" and unbolt. Once the bolt is loose, hold it tightly and pull it out. "Coil on plug" will also come out. This "Coil on plug" is also difficult to pull out especially the one near the driver side but it will come out eventually
3. Using 5/8" spark plug socket, unbolt the spark plug and take it out. When you can no longer turn the extension by hand, use a precision torque wrench and torque the plug to 18 ft-lbs.
4. Follow steps 2-3 on the passenger side but be sure to remove the intake box in order to gain access to "coil on plugs"
HOPE THIS HELPS!