FYI - It's a LOT easier to build a preamp with an op-amp than with transistors. You can make a preamp with an op-amp and two resistors. You can make a buffer amplifier (an amplifier with a gain of 1.0) with an op-amp and no other components (except for a couple of bypass capacitors, and of course a power supply).
What are you planning to do with the Arduino? Are you trying to use the Arduino as an effect box/pedal, or are you making a lighting effect or something like that?
The signal from an electric guitar is somewhere around 1V, so you don't really need to amplify it. However you do need to deal with the negative half of the signal, and it wouldn't hurt to use a buffer amplifier to isolate the guitar signal from the Arduino and the negative-voltage protection circuit.