The temp gauge issue would likely be electrical. The AC issue can be a number of things and it is best to get it checked by a technician to get this problem diagnosed correctly.
check the manual if your oil is a lifetime,
if your car ran for 40,000 - 50,000 the u must change it now but not if it ran for more then 100,000 KM you just change the transmission itself after 150,000
and if its not a lifetime transmission oil then u must change it after every 20,000 km.