First, if your heater fan works only on max speed, likely the cause is not the switch, but the fan resistor. suspect of the switch if you need to wiggle it to make the fan start, or if the positions seem to be "rolled around" - both did happen in my case.
You do NOT need to remove the heater controls panel, fortunately. Do not try removing the controls panel, it is a nightmare.
Steps are actually almost the same as for replacing the light-bulbs of the heater panel:

1) Remove the stereo: The is a special tool for that, but can be improvised with four long needles, I used a BBQ metal sticks from a 1 euro shop. Once the needles are as deep as they go, you need to pry the radio out from sides, can be quite hard, just keep trying.
The stereo can be safely unplugged, when you plug it later back it will not require any code as long as you plug it into the same car, seems

2) remove the ashtray: Just open it, unscrew the two screws you find and remove it. Note: Even if you do not have the star shaped screwdriver needed for these screws, you can just use a flat screwdriver of a width that just fits into the star points. Next picture was taken after the ashtray was removed:

3) Remove the heater knobs mask: There are 3 tabs on top and bottom, lift them with a thin, flat screwdriver. Careful, they can be broken easily.
In the above image you can see the bottom tabs - I already broke the rightmost one, but the remaining ones were sufficient :)

4) Pull out the knobs - no screws, just pull on them till they go.
5) unscrew one small Philips screw holding the transparent plastic light ducts. Now, you can remove the transparent plastic.
You can replace the light bulbs at this point - just pull them out and plug in the new ones, see the bulbs in the picture below. Replacing bulbs was already described in a separate guide.
6) now you see the switch of the central knob - it holds in place by two small Philips screws. Unscrew these and the switch can be pulled out, dragging a cable with it. Unplug the cable - and the switch is free now:

The switch only states "B837 12V" on it.

I managed to open the switch and fix it partially, cleaning the contacts, however I am still pending of getting a replacement from a scrap. Stilos are relatively rare, however it seems like the more common Punto Mk2 and Mk3 does use the same switch model. I will post update when I get one :)
Sorry for not taking pictures of all the steps, if anybody finds this guide useful I will try to get more pictures next time, as I need to do it all again when I get a spare part.

Cheers, Roman
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