P.S. Sorry for my English. I am from Croatia.
-Soldering iron and some solder
-Wire clippers or any other cutting tool
-Foot switch (I found mine in my workshop)
-10k pull-down resistor or you can use one integrated in arduino
Computer with Linux (I am using Debian stable (Sid) with XFCE), python with installed serial and OS module and, of course, the Arduino program.
Step 1: The pedal switch
First you need to open it and find contacts for the switch.
If you have NC(normally closed), NO(normally opened) and COM(common). Use the NO and COM.
Strip the isolation form the wires off.
Now connect the wires to the NO and COM connectors and close up the casing.