Black tape on logicboard important?

I can't speak with certainty on this but my initial feeling is: if you found black tape originally underneath that Airport Extreme Card then I would say go ahead and replace it with the exact same type (there are 2 different types of black tape). Remember, the shinny soft plastic black tape have a very "sticky" adhesive on it and you DON'T want any of that to get into/near any connection points on any part of the logic or I/O board.

Black tape serves and an insolation between electrical components, if electrical metal connectors/wires are extremely CLOSE to any metal body ground an "arc" can occur (depending on the voltage that goes thru that component) which can damage some sensitive components and or cause a SHUTDOWN.