Sounds like the both of you got screwed big time !!!
The display is an LCD and as with all LCD's (Including Modern TV's) the main failure is the display edge lights.
Carefully remove the oval trim by inserting small bladed screwdivers down and behind the extreme ends of the oval.
You should NOT need excessive force !!
Remove the oval trim and reveal the two 'torx' screws holding the instrument display in place. Remove them and gently ease the whole display forward and tilted downwards to see the printed circuit board on the back. You should be able to determine from the front the approximate location of the bulb holder which resembles a small plastic lump with ridges running down each side. Firmly grip the holder and twist it anti-clockwise very lightly by about a half turn,you should then be able to withdraw said holder and bulb which when held up to the light will most often reveal a burned out filament or be blackened.The replacement bulb is an open wired glass envelope type and referring to the invoice for those I just purchased from my main Citroen dealer would appear to be called "Z2type" bulb holders and are approx @£1.50 + Vat. A huge difference to what you guys have paid.
Sometimes the bulb comes with the plastic holder and others are bare, all you need do is pull the bulb forwards out of the existing holder and replace with the new one.
Steel Wheels, February 2008