Yes there are 3 light bulbs in the OBC. The procedure for changing them is quite easy.
Take out the radio, reach in to whole and on the upper left side of the OBC you will find a lever which by pulling it releases the OBC. Chech the light bulbs (one on the left side of the OBC, one on right and one on the bottom), two from the sides are a backlighting for the LCD display and a bottom one is for the buttons.