If your looking for a headache, try and pull the heater.
The a/c and heater is all in the one box so your going to have to crack the a/c gas lines. The box itself takes up the entire passanger side right across to the drivers leg.
You can undo the sides of the dash and the 5 screws that you'll find under the plastic strip that covers the join between the dash and windscreen, that in itself is a mission, it's got clips in the middle and a screw on each end. (i broke mine)
The dash should, after a big effort, sit on the pass seat, i left the steering wheel and turned the dash sideways.
The bolts that hold the box in place are also used to hold the wiring harness in the engine bay. In fact most of the bolts that look like that are part of that heater. Access is much easier with the head off especially when your putting it back
It is a big job and i'd put aside a weekend for it.