depends on where the leakage is

if the leak is due to trans pan, you can replace gasket to get it fixed. but sometimes, the leak could be in fluid level tube-end or kickdown plugin; also could be at K1 or K2 cylinder (in this case, the O-ring is hardened, you would need to replace it... Some can be changed while tranny is on, while some do need to lower the tranny; you can see latter is labor intensive, the price varies.