It's not easy as it requires the removal of the dashboard. I've done it twice.

It should be on the CD as it is in the book.

If I recall correctly:

1) Remove center console.
2) Unplug airbag module under passenger floor matt.
3) Remove steering wheel.
4) Remove instrument cluster.
5) Remove A-pillar trim.
6) Remove dashboard.
7) Remove clips holding heater box together, remove cover.
8) Remove heater core.
9) Reverse procedure.

Good luck!

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)