cooling system

[clabcon]

I know the air con is not the e36 is its coolest pointed, however had all the obvious regas and filter change but still had a insufficient airflow from the central vent at max fan speed. took off the vent to discover the plastic behind the back had been hacked away and most of the air was flowing to cool the radio below!

realoem suggests changing the ducting behind is an involved job involving dashboard removal:

http://www.realoem.com/bmw/diagrams/e/h/17.png

has anyone done this before and can comment about the extensiveness of the pipework thats needs to be replaced?