Coix:
Just to make sure it is "J3" we are talking about, right?Seeing as i dont have an oscilloscope, should i just try connecting to J3.
Yes, J3.
If you have a multimeter you should check the voltages on those pins. If it's an RS232 connector they'd may have high voltages or negative voltages that can harm the Arduino. If they all read 0 or +5 it should be safe enough to connect.