the lens does not come off the cornering light bucket. it cannot be taken apart (I've tried.) you have to remove the whole assembly (not hard at all)
99% of the oxidation (yellowing/ hazing) is on the outside anyways. if there is dirt on the inside, you can put hot water and dish soap inside the bucket and swish it around, then rinse out the soap and get out the remaining water with a hair dryer but thats more of a PITA than its worth IMO.
the cornering lights are very easy to restore. I used a mothers headlight restoration kit (pretty much any brand will do.)
first, take off the plastic chrome trim around the headlights (6 torx screws hold it in 2 on the side, 2 in between the 2 headlights, and 2 on the inside corners of the trim- sized T25 or T27 if I remember correctly.)
once the trim is off, remove the cornering light bucket (has 2 hex bolts- don't remember the size.) remove the light bulb sockets (twist out). you now have the cornering light bucket off.
get a pail of water and some 1500 grit wet sandpaper (if kit comes with sandpaper, use the 2 finest grits- don'tuse the rougher grits- they do more damage than good)
wet the sandpaper, scrub in small clockwise circles. keep the sandpaper wet (you will feel the friction when it starts to dry out.) occasionally wipe off the lens with a towel and check your work for consistency.
after you sand off most of the yellowing, put the buffing pad in a power drill. apply a nickel sized amount of polish off center of the middle of the pad. press drill against light bucket, start drill slowly (1/2 trigger at most) for a few seconds (this keeps it from slinging polish at you.) then press the trigger down all the way and move the drill in a small clockwise circle. once the polish has worked in most of the way (you can feel the friction when the polish starts going away) apply more polish and repeat. after about 20 minutes, you'll have a new looking cornering light bucket.
