[me and my metro]

I looked through all my Photobucket pictures and I no longer have those pictures so here goes. You are going to cut and extend one existing wire. You are going to attach both halves of that wire to the switch. The switch has three posts and works like a three way house light switch. That type of switch is usually used in your house on stairway lights one at the top and one at the bottom. You are going to connect the part of the wire from the computer to the center or common post. Connect the part of the wire from transmission temp sensor to one of the outside posts. If you did not hook up a wire to the other post the switch would just make or break the circuit.
Solder the resistors end to end to get to the resistance value you want, I would want some value that works and the computer will believe. Add wire to both ends of the resister string long enough to work with, cover securely with tape. Connect one end to chassis ground preferably where another ground attaches. Connect the other end to the switch. Now when you flip the switch the computer either sees the actual temp in the transmission or the fixed value of the resistor string.
I would start each day with the switch in the factory configuration until you need overdrive. Then flip the switch, if you drive far enough to warm up the car flip it back. Repeat....
I hope this helps.