There is no easy way to do the plugs as i have just done mine today. When changing oil filter, make sure you disconnect the pick up sensor behind the crank shaft pully, then fill the oil filter first, then put on the oil filter. When the oil filter is on and there is oil in the engine turn the engine till the oil light goes out. (Engine will not start as long as you disconnect the pick up sensor.) When oil light goes out then reconnect the sensor, then check oil levels.
P.S Thats what i got told to do with my WRX and it is running sweet. I got told they do this at the Subaru garage.
(Wullie)
Hope this helps you out!!!