If you mean MIDI to 1V/ octave CV you'd be amazed how many people have already done such projects with Arduinos. If you were to Google "Arduino MIDI to CV" you'd find all sorts of useful information.
BTW an 8 bit DAC isn't nearly good enough if you expect to get musical notes out of the synth. You might get away with 12 bits but really 16 bits is more like it.
Steve