How do you change the bulb on the dashboard information unit on a peugeot 307?

If you mean the multi display unit on top of the dash, it couldn't be easier. Push the unit upwards from the side nearset you (it may need a bit of a hit) and pull the unit free. There is multi-plug fitted to the unit which can be removed (if you do remove it you will need to re-set the display info - clock, date, radio channels etc). The three bulbs are situated along the back of the unit and are of a twist fitment, you will need some long nose pliers to make this easier. One of the bulbs will have to have the multi-plug removed to gain access to it. From experience, it is easier to change all three bulbs together. I hope that helps!