As the enclosure is made of FR4 (PCB material), all electronic components should be soldered first, as it will be harder after the whole enclouser assembing.
Program the MCU (software is available at http://www.voja.rs/projects) and then measuer the voltages at DC-DC convertor outputs (9-9.5 and 4-4.5V). DC-DC convertor will not work if MCU is not programmed and running.
Check if the noise signal is present at MCU AN0 input (you can use oscilloscope or, if you don't have one, you can also connect it to PC speakers input to hear the noise).
When everything works OK, solder all mechanical components: spacers first, and then enclosure walls. Enjoy!