1989 buick lesabre knocking sound?

I have a 1989 buick lesabre which has been sputtering a little bit for a few months now... Today after getting it home I started to hear a clicking sound that's pretty loud when outside of the car, I checked the oil and it was around a quart and a half low( i know, i know). I asked my brothers opinion and he said it's either a rod knock or the harmonic balance.... based on the information given can anybody help me to diagnose this problem and tell me the easiest way without a shop to fix it, thank you!