Unless you are fully able to carry this work out yourself then please do if you have any doubts call a qualified electrician.
If the switch is the cause and not a blown fuse or a tripped MCB then the job of replacing this is straightforward just so long as you pay attention to where the wires are fitted inside the socket.
These switches are not usually cheap.
Just make sure that all power is off before you attempt to remove this switch.
The bulb blowing will not stop the switch from working but then again you would not know if the shower was off or on.
Carlito
October 2007