Typically, there is a overrunning clutch for cable up. Brake pack then doesn't release on cable up. You need brake release for cable down, that's why you have all the pressure on cable down, it has to provide enough pressure to overcome the spring pressure on the friction disks, to cable down. As mentioned above, most of the time the seals go on the brake pack, putting hydraulic release oil into the gear oil of the winch. Shouldn't be anything exotic for seals. Unless the frictions are bad, I never replace them, I doubt yours has done enough lifting to wear out a set of disks, plus those will be hard to find. If it's been sitting, it doesn't surprise me to have a leaking brake pack. Just be sure to drain and refill the gear oil in the winch, removing the hydraulic oil that's leaked in there.