I replaced mine radiator (745 turbo) a while ago together with hoses, thermostat, and plastic coolant expansion tank. Some people also change the water pump at the same time. I do not remember significant amount of tranny fluid spilled during the process (there will be some left in the old radiator.. so you might need to top it up). Indeed disconnecting the tranny fluid lines is the major issue, so you could do radiator change and fluid flush at the same time (your mechanic will most probably disconnect one of these lines when doing the flush)... Good luck!