Michael,
Try this, and change the 10k preset to a 2,2 or 4,7k preset and adjust the voltage on output to approx. 1,5 volt.
A 2,2k preset resistor= approx. 0,7 mA and 4,7k= 0,3mA current from your 3 volts source.
Because this low voltage circuit only can handle 1 volt with approx. 50 kohm load before clipping, and a guitar with high output pickups can give a lot of level over a hi-Z input, so maybe you must have a -10dB pad before the FET transistor input, (2,2 Mohm with a 18 pF capacitor in parallell and connected in series with the input) or turn down the volume knob on your guitar.
You can find the pad circuit here on my API 312 DI-modification
http://web.telia.com/~u31617586/#Bo%20Hansén's%20audio%20circuits%20design%20talk
Here is the orginal post that the circuit was use for from the beginning
http://www.groupdiy.com/index.php?topic=4187&postdays=0&postorder=asc&start=30
BTW, there are a lot of nice "rail to rail" low volt op-amps and buffer from Maxim that is made for small computer or telephone equipments with voltage feed from battery or USB interface.
--Bo