burned out "idiot light" bulb

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'02 Mazda Protege5
I just noticed that when I first turn the key to ON before starting the car the oil pressure warning light doesn't turn on anymore. doesn't seem like a big deal until i'm driving and I lose oil pressure but I don't realize it until it's too late because the light never went on. not that I expect an oil pressure problem, but I assume the bulb is just burned out? anyone know what size bulb it takes? also, while I'm in there I want to change all the bulbs to LED. is the cluster a b**** to remove?
 
I don't know about the bulb but here's how to remove the cluster.
Looks real easy.

 
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