He's made a great job of it, and doesn't look quite as complex as first imagined:-
"here is how to do it
1. Jack up the car and remove rear wheels
2. Remove the wheel arch liners.
3. Drill out the plastic rivets on the old grills and pull them off. They are stuck with double sided tape so take a bit of pulling.
4. Offer up the turbo vent up and see how it fits. The flat panel behind the door is just bonded in place and if you look round the edges you can see it comes away.
5. Working from inside the wheelarch jam a pry bar down the back of the cover levering it off but be carfull not to puncture the clam. Keep
doing this till the larger section can be taken off.
6. Now offer the vent up again and see how much has to be taken off the back of the clam section to
allow the vent to sit nicely. I trimmed it away using and air saw but a coping saw could be used. NOTE: Make sure you only take away a small amount at a time offering the vent up all the time till it fits nicely.
7. Once done sand away any bonder left where you pulled the blanking plate off and spray it black as you will see it through the vent.
8. Fit the vent in place and drill two holes for plastic push rivets to go through (one in the door shut and one at the top of the vent inside the grill).
9. Tape the back of the vent tight to the clam so there is no gap and bond it in with a strong bonder like windscreen bonder, they are bolted in at the back edge on the turbo but the studs are not present on the n/a.
You won't need to do any paintwork if you are careful, other than the vents themselves.
Hope it all makes sense and good luck."
And the pics...
Came off in about 5 pieces 
