If you are doing this to change the heater matrix, now is the time to clean the surrounding air ducts.
Reach behind and ensure the speaker wires, clock wires, and airbag harness are all free.
Pull the three rotary knobs off. Remove the screws behind them to loose the heater control panel. You do not necessarily need to disconnect the cables; you can often push the unit back into the dash cavity.
Reconnect the instrument cluster and battery to test all lights and switches before putting all the trim back on. If you'd like more specific help, tell me:
Slowly pull the dashboard toward the rear of the car by about two inches.
There are usually two or three 10mm bolts located under the scuttle panel (where the wiper motor sits). You must remove these to release the dash from the firewall.