Idling issue and fluctuating engine temperature

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Lets start with the first question. The first thing I suggest is to simply have the computer scanned to confirm that the problem is the same as the first time.

Here is a video on how to scan your vehicle:
https://youtu.be/b2IJGfImVvw

Once you complete and determine the sensor is the issue, I would first try cleaning the sensor. Different climates can have an adverse affect on these sensors. Here are the directions for that process:

https://www.2carpros.com/articles/mass-air-flow-service

Additionally, here is how the component works. When checking yours, make sure the connection is clean, tight, and undamaged.

https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf

Here are the directions for removal, servicing, and replacement of the component. I have also added pictures specific to your vehicle.

SERVICE PROCEDURE:

1. Remove the top of the air filter box with airflow meter assembly from the vehicle
2. Remove the airflow meter sensor from the airflow meter housing.
It's held on with 2 T20 Tamper Resistant Torx(R) screws.
3. Thoroughly clean the air filter box and the airflow meter housing.
Wipe out the entire inside area of the airflow meter housing with a clean rag (see Figure 2).
Use low-pressure compressed air or a shop vacuum to clean out all dust, dirt, and debris from inside both halves of the air filter box and inside of the airflow meter housing (see Figures 2 and 3).
CAUTION:
Cover the ducting from the throttle body with a clean shop towel or other method so dirt or debris cannot enter the engine intake manifold.
4. Install the new airflow meter sensor into the old airflow meter housing (see Figure 1).
Do Not replace the entire airflow meter housing; replace only the sensor listed in the Parts information.
Tighten the screws to 1.2 - 1.8 N.m (0.12 - 0.18 Kg-m, 11 - 16 in-lb)
5. Reinstall the top of the air filter box with the airflow meter assembly back into the vehicle with a new Genuine Nissan air filter.

As far as the overheating issue, please re-post that problem separately

I hope this helps. Keep in mind, even new parts can be bad, so there is a good chance it just went bad again. Additionally, it is imperative that you keep the air filter clean as well as the air box and induction tube. The sensors are delicate.

Let me know if you have other questions.

Thanks,
Joe.