http://www.subaruoutback.org/forums...orums/99-do-yourself-illustrated-guides/20574-2002-obw-front-oxygen-sensor.html

Will be extremely like this. You'll need an oxygen sensor socket or a crow foot style socket, lots of PB Blaster or your favorite penetrant oil of choice, and probably some bandaids if you have bigger hands.

Brush up on creative combinations of profanity if you have any rust.

 

I got the O2 socket over the sensor and then the wrench on but it became stuck tight against a sump. Be sure there is room for the socket and wrench, in the end a large spanner on the socket worked better for me. I learnt that disconnecting the battery reduces intermediate trouble codes too.

 

Update: Replacing O2 sensor (Air Fuel Ratio A/F Part # 22641AA280 on 2004 Forester

UPDATE :
I ordered Subaru OEM sensor Part # 22641AA280 on E-bay for $45/ and got it installed yesterday from an Indy who charged me only $60/ and there is no P0032 code

Happy that my cost to fix the check engine light was only $105 = $45 + $60

For those interested in buying Genuine Subaru parts at a very reasonable price seller's E-bay ID is 'reload796'