Keep in mind some temps you see listed are:
1. Lower mileage than yours.
2. Different trans than yours.
3. External coolers.
4. Temp senders in different places/external gauges.
Alot of variables. Knowing what I know about your area, you're a prime candidate in my book for an external cooler. Please bypass the core in the radiator when you do this. It get'* clogged over time, especially after a trans failure (very small passages in there).
A viscosity-controlled cooler is best. It won't flow out of bypass until the fluid warms up to a pre-determined temperature/viscosity.
You'll find the plug for the sender very near your shift linkage on the top of the trans case (just inboard of the end cover) under your TB. Keep in mind some heatshielding will be needed to keep that from picking up ambient heat from the crossover. I still get false-high readings on mine, but I'm used to it, and know what 'normal' is. You're looking for a small hex plug, not the free-spinning pressure vent.
Top of the trans case, cruise servo actuator in the right background, looking front to rear on the car. White wire is the sensor.
another view from farther out showing the old sensor I ran for awhile:
Keep in mind the factory sensor is inside the valvebody and will read a slightly different temperature than this location. Imagine the crossover pipe being installed in these pics just to the left of the sensor location.