Transmission cooler line connection going into cooler is very corroded....can it still be replaced without replacing major parts ? Like the cooler itself or the radiator?

Unfortunately we won't be able to answer this 100%. It's very likely if it's rusted that the line and/or cooler can break when you try to disconnect. Use some pb blaster or wd-40 and be gentle but prepare for the worst. Alex

IF the penetrants do not help .. Have auto repair facility use acetylene torch to heat the line *flare nut* - it should turn easily then. Otherwise radiators aren't all that expensive.