Here we go , this was done by Simondo, great in detail.
Hi mate,
There is (was) a guide on the main site but obviously that's not accessible right now.
It's a wee bit of a pain to do because you NEED patience and patience isn't my strong point!

1. Take the side lights off the car and remove bulbs and wiring.
2. Get a (wide, if possible) flat head screw driver and a philips head.
3. Boil the kettle (you'll need to do this several times.)
4. Submerge the side lights in the hot water. This is to soften the glue.
5. Top up the water as it cools so it remains hot.
6. Once the glue that holds the casing to the lens has heated up enough you should be able to start prizing them gently apart. There are bits all around the light the you need to un-clip. You'll notice these when you look closely. Take your time. It's easy to damage them (Especially if you've not given it enough time to heat up.)
7. Eventually the pieces will comes apart.
8. Unscrew the two philips screws the hold each of the orange bits in place.
9. Heat the glue up again either with hot water but preferably with a hair dryer or heat gun as this will give you a chance to properly dry the side lights. Once the glue is warmed up push the parts firmly back together. Again it's all too easy to break something here so be careful.
10. Once they're properly pushed back together you're pretty much done. You just need to ensure they're dry. (The last thing you want is condensation) Whip them back on the car and put in some silver bulbs that flash amber (although to be honest I never bothered with these.)
Hope this helps.
Simon.