Sorry to be a little 'picky' here, but there are 4 bulbs and holders inside the ACC control unit. I should know, because I've got one open in my hand now!
Small and insignificant point I know. I'll slap my own wrists and get my anorak on!!!
Sgould's post refers to the 9-5 ACC. The 9000 ACC is quite different. In the ACC2 units in my '95 and '96s, there are three bulbs, accessed by removing the six cross-head screws securing the front panel and unclipping the panel. Older units may have a different number of bulbs.
The bulb holders can be removed by turning anticlockwise. You can simply throw away the entire bulb/holder assemblies and replace with new units, available at your Saab dealer for loadsamoney, or remove the wire-ended bulbs from the holders and replace with part number WQ13 from Maplin at 79p each (or £6.70 for 10).