Umm, I should know this I replaced some in the summer!
My Vectra has 509T bulbs in various power ratings, but I think the Sprinter uses bigger bulbs, maybe 501 (typically also used for sidelights) Can't recall if the backlights were different to the warning lights now (they are in the Vectra - I have had that panel out several times!), I do know my ABD fault started at exactly the same time as I put a bulb in the empty holder behind it....
I didn't find the instrument panel very difficult to get out (watch for that captive nut on the fuse board spinning so the bolt won't come out though) so you could fairly easy remove it for a gander. They are common bulbs, I replaced them in Halfords as far as I remember, or are you think of upgrading to coloured LEDs?
Actually, I think the Sprinter has some 509Ts as well, I seem to recall raiding the bag of ones I took out of the Vectra when I switched it to LEDs (more trouble than it was worth!)/
Jim