Finding out capacitor polarity on pcb
This looks like a completely passive circuit. There is no actual power to any of the components, just the audio signals coming in and going out. The only reason for the power on pins 6&amp;8 is to power the LED. 

You have two separate channels coming in on Pins 1 &amp; 7 and going out on pins 3 &amp; 5 (or maybe the opposite direction). CF07 and CF08 are just to block any DC difference between the input audio signal and output signal. This will depend on the rest of the circuit it is connected to.

I suggest you power up the circuit, and just use a voltmeter to read the DC voltage across CF07 and across CF08 . Install the caps to match any voltage you measure. If you don't see any voltage with the circuit powered you could wind the volume up and down and see if anything changes. If the voltage is always zero, then flip a coin :-). 

Failing that, My best guess is that as pins 3 &amp; 5 have a connection to Ground, they will tend to be at zero volts. The input on 1&amp;7 is most likely to have a positive bias (if any), so I would suggest connecting the caps with CF07+ to pin 1 and CF08+ to pin 7.