Any tips for replacing a heater matrix? (306)

[Danez]

I need to replace the heater matrix in my turbo diesel 306 (Coolant found in the passenger footwell, blower reeks)
Looking at the haynes manual it seems simple enough if not time consuming a tedious. but I'll give myself a few days to do it.

Just wondering if anyone here has done this and has any wise words before i start ripping apart the dash!

cheers