Well if it's like the control unit on my 740, then yes, yes you do have to remove the control unit from the dash. It's not terribly difficult as you only have to pull it out maybe 3 inches or so to get at the bulbs. The radio will have to come out along with the trim piece that surrounds it. There are two bulbs that are on top of the unit, mine were covered by a strip of electrical tape. They just twist out. Now for replacement bulbs, I've no clue where to get those. I tried getting some from my ind mechanic and he couldn't see a part number on 'em so he didn't think he could order them. Maybe you could go to a dealer and they could charge you, say, $20/bulb. Or you could solder in a clear LED or maybe a colored one if you so desired. Anyways, let me know how it goes!

-Greg