I am currently involved in an academic project which the topic is to 
design a Digital Tuner for Electric Guitars. My knowledge of electronic 
is very basic, so here I am.

I need to pre-process the signal that goes out from the pickups of a 
common electric guitar, let's consider passive pickups so....we have an 
output voltage from 200mV up to 1V of peak, with also negative peaks (of 
the same magnitude).

I have to use the STM32F4 (Discovery 
Board:http://www.kynix.com/Parts/3597871/STM32F4-GAME.html), so I need a 
very simple circuit that drives the On-Board 12-bit ADC, that takes, as 
inputs, signals with voltage between 0 and 3.3V. So I have to design a 
pre-amp circuit that amplifies and clamps the guitar's output.

I want to underline that I have never realized an electronic circuit (a 
real one, not in the simulator) before. I am wondering about:
STM32F4 provides some voltage sources (5v or 3v). Shall I use these 
sources or is it preferable to go with an external voltage source (e.g., 
batteries)?
I have chosen an opamp that is not, let's say, "handy" because it needs 
2 voltage sources: the TL082. What op-amp do you suggest me to use? 
(maybe with only 1 voltage source)
I have tried to design a circuit by using LTSpice, but I don't know if 
it is correct at all. You can also notice that I have inserted a 
filtering stage (LP w/ cutoff freq. 2,2 KHz) and a "protection" Schottky 
diode before entering in the pin of the board.