I have a 2003 and do all oil changes my self. I have yet to change the plugs and wires so I'm not sure with that. With oil changes ramps are nice to use. Make sure your getting the oil filter cause on the Forester the trans filter looks like a oil filter. The trans filter will have writing on it stating trans filter. Make sure to look for the right drain plug too, cause there is a drain plug for the front differential in the "general" area. The drain plug for oil is a 17mm hex head. When I first got the Subie I took it to a fast change oil change place and they removed the trans filter and drained the front differential, after that I did every one my self.
The air filter is easiest to me if the whole box is removed. 1 bolt on each side and loosen the clamp. Unplug the sensor and plastic tubes. Push back the box and lift up once it clears the air intake.