The symbol is stored in TOS. If you have a German Tos, it will come out the German money symbol.
The keyboard just sents the GDOS ASCII position that will translate to ASCII code. I mention GDOS ASCII because I remember reading somewhere that states there is some difference between it & ASCII.
Anyway, think of it as coordinates where the key is pressed. This is sent to the computer and it figures that the particular coordinates produces a particular symbol. The symbol, how it looks like, is hardcoded in the TOS.
So you have to replace the German TOS with US TOS or British TOS. IIRC,the British TOS has hoth the £ and $ symbol.
You also need to change the keyboard keycaps to represent the symbol you want.