Not a very hard job to do...
I just swapped plugs on '01 Forester n/a with 90k which I bought a year ago. May have been original plugs -- electrodes vaporized to a pin point! Anyhow I'd put off the job due to negative forum chatter. But it's not hard, should be 20 to 30 minutes per side -- faster for gear heads. Only added tasks are: pull the resonator assembly (as one piece) on passenger side by removing 3 bolts ; pull the washer reservoir on driver side by removing 2 bolts. That's the added work. I chose to just pull off the 2 washer hoses and lose a few drops of fluid in the process. And I disconnected the 2 electric sends to the pumps. For the actual job I recommend a 5" socket extension plus a 2 or 3" extension. The 5" reaches the plug and sticks out about an inch or two... perfect. NOTE: you must pull on the boot 'tabs' pretty hard to release from the plug (hence the advice about using dielectric grease in the boots), and in fact I tore one boot in the process. Therefore, it MIGHT BE worth it to spray a little silicone in there before pulling with all your might, however that may not affect the problem which is likely at boot/plug interface.... therefore some GENTLE TWISTING may be more appropriate. Only regret: wish I hadn't been so spooked by those posters ! No worries.