x2
only way lines get gunk in them is if someone adds it...
a leak will pull water into the system when the pressures are very low.
water will interact with the oil and the refrigerant causing gunk! and more leaks.
if you have original 12 in the system, you are VERY lucky! (odds are good that if it's still 12, it's been topped up over the years.
anyway, I'd start with a set of gauges and see what the pressure is sitting at.
if it's above 100psi, you should be good on charge, time to follow electrical issues.
if it's below 30, you have only a touch of gas in there, and you will need to remove it and or pressureize it with Nitrogen, or some other dry gas, like CO2 or Helium and start looking for leaks.
once the leaks are found, you can decide if you want to fix them, replace the hoses, or flush and repair... of course, if it's below 30, but still pressureized, above 0 you can just add in 12 and go... but you will be knowingly filling an R12 system that has leaks in it...
if you can handle that on your conscience, I'm good with it.