I plan on installing an external trans cooler and fan since I did the radiator cooler bypass and decided to call a few places in the area to see how much they'd charge to flush the transmission on my pathfinder. Here are the results:
1) Independent shop: "We don't service Nissan transmissions because we had a couple instances where the radiator and transmission fluids mixed." I told them I bypassed the radiator cooler and they still said they wouldn't take it in.
2) Nissan dealership A: "It'll be about $225." I asked if they'll be using Nissan Matic-J or S, and the service rep said, "Oh, I forgot... it'll be closer to $275 because of the Nissan fluid."
3) Nissan dealership B: "$189.99." I asked what ATF they use and the service rep said, "... the BG equivalent."
4) Nissan dealership C: "$199... it's a kit, full flush, Nissan synthetic ATF."

Looks like I'll be flushing the transmission myself.