Transmission cooler lines leaking

[earnies2]

I noticed my transmission lines are wet.. not leaking but they need to be replaced. I was thinking on adding a cooler like on Freightliners have on the frame behind the cab. So I would come out of the trany go to the cooler behind the cab then to the cooler in front of the radiator then back to the transmission is that a good idea and will it help to keep the transmission cooler? Is it worth it? I need to replace the lines and I think I have the cooler in the shop so the only expense would be the extra lines and fittings.