Over the summer I embarked on multiple projects and upgrades for the g37x sedan. One project included doing some slight upgrades to the AT as a supercharger is planned as a future project. I wanted to address not blowing the trans at around 500hp, so I decided to do an external trans cooler and do a valve body upgrade. Suffice to say a trans flush was in order as I'm sure it was never done before. This will be more concise as other posts cover much of the details, but I thought I'd share some tips to make things easier. Download the FSM from a reputable website. I followed Nissan's instructions as close as possible. First I obviously drained the fluid using the pan's drain bolt and replaced the drain bolt. Removed the pan, and started unbolting the VB unit. But the way, much fluid is still retained in the VB, beware. Sent the VB to IPT transmission for the upgrade.
Ok now for the cooler.
I used the czp/z1 notion of oil cooler upgrade as inspiration. Bought my own coolers (3), lines, and items necessary for oil, trans, and power steering cooler.

Right 34 row oil cooler Left 25 row trans cooler Front 10 row power steering cooler Custom brackets made for mounting
I used the mocal/setrab sized cooler from Derale. The passenger side area was too narrow to fit the 235mm cooler due to some AC components, so i used 2x2 L-brackets, flipped it around, and mounted the cooler slightly forward. In the end it worked out, but a 115 matrix or some other narrow cooler would have fit. I wanted a thermostat adapter to bypass the stock cooler which is in the radiator. This allows it to warm up even faster but stay much cooler as it is no longer relying on the engine coolant for heat transfer. Space is limited but I found a decent spot to mount the thermostat.

This unit opens at 200°F to circulate fluid through the cooler. Below this it just takes it back to trans without cooling.

⅜ npt to 6an adapter. 6an lines out to cooler.
This spot clears an undershroud upgrade (TBW) with some trimming done to the mounting bracket. The stock rubber lines were tricky. They seemed to be 3/8 but they are not. Much smaller. Stock lines would not fit over the ⅜ barb. ⅜ line was way to big for stock trans hard lines. My immediate solution was finding 5/16 line at O'Reilly's and getting both side to fit. So far no issues.
When the VB shipped back, I installed and filled with valvoline max atf. I then used the procedure spelled out in Nissan/Infinti FSM. To make it easier to do, I went ahead and purchased a separate fluid transfer pump so I don't mix oils with gear oil pump.

Purchased at Menards. Uses 12mm tubing.
The overflow is used for filling, that bolt is an M8 x 1.0 thread. The FSM says to purchase a special nissan tool for filling. Then you'd have to remove it, replace bolt and run engine. Well I didn't see online any authentic oem adapters, and read some times they break anyway. Here was my solution.

Special adapter to ball valve to tube adapter
I bought both adapters online, and picked up the ball valve at a local hardware store. I believe it was M8x1.0 to 1/4npt and the other was 1/4npt to 12mm quick release or whatever they are called. I closed the valve during the engine run procedure an only opened when pumping the fluid in. This was done 3 times as suggested and a final top off after actual driving was done. All in all I used about 7 gal of fluid. They are much cheaper at a supermarket than the auto store. Hope this further helps for those with auto trans and especially for AWD Gs.