Oh yes, the 328p should be clocked at 16mhz . It's the easiest configuration, and you can program it as if it was an Arduino Uno! Look at a pinout of the 328p and you can see where the xtal goes.Of course you can set the fuses of the 328p to run at a different rate using the internal clock and everything should work just fine.Check out more info on Biodata at electricityforprogress.com/Forum
In order to test, you want to have one electrode connected to Pin 2 of the 555 timer and the other electrode on Pin 7. Check out the support forum at electricityforprogress.com/Forum
I do have a couple kits left on my store https://squareup.com/store/electricityforprogressThere is more info on the support forum http://electricityforprogress.com/Forum
Any input Jack should work. The sleeve of the Jack goes to one of the probe input pins and the tip of the Jack goes to the other probe pin. No ground involved with the input Jack.