Add $120 for a battery and you are getting pretty close to the price of a new P2. I am guessing this is one that has been flown and crashed, damaging the gimbal and battery? Is this the sort of quad you want to take on?
Pros: 2.4Ghz FPV gear has better range for a given power level over 5.8Ghz.
Cons: You cannot use the gopro wifi for FPV, as the signal is not strong enough. 5.8Ghz FPV is now very widely available and you will get far more choice. 5.8Ghz radio gear is pretty much specific to DJi and does not have the range of 2.4Ghz, particularly if you fly around the back of a building or large tree and lose sight of the bird.
Personally, I would spend the extra on a brand new P2. It will also be easier to fit the FPV and gimbal as all the correct wiring will be in place.