Do you know what brand of sensor Autozone used? The 4runner likes OEM/Denso sensors.
"A/T oil" is short for Automatic Transmission Oil, so the light refers to the tramsmission fluid rather than the engine oil. Pull the transmission dipstick ( on the passenger side of the engine bay, near the back) and check the fluid level and color. Hope for red, not pink and foamy. Hopefully you just need to add ATF (auto trans fluid) If you need to add fluid purchase anything that is DEX III or higher like DEX IV, V, VI. I like to use Mobil 1 synthetic ATF, they sell Mobil 1 Synthetic ATF at Autozone for $10 a quart. It is ok to add synthentic ATF anytime.
Also look at your radiator overflow resivoir. Traditional Toyota coolant is red and there should be some in the overflow after you drive and warm up the car.
The stawberry milshake is when you have a radiator failure and the trans fluid mixes with the radiator fluid. It happens on 1998 and 1999 4runners and it is bad news for the transmission. I don't see it as much on the 2000 4runners.
Edit Adding....Of course where you have you car serviced is a personal choice. However, I would not take a 4runner to Autozone for service. Sure, I'd take my old GMC Jimmy there but the 4runner should be serviced by a dealer or someone familar with them. They are great trucks and will drive forever if maintained but they really like OEM parts and you can't get those at Autozone. Just FYI