16 Dart SE with the 2.0 engine. I've got 90k miles on it. I drive it 50 miles a day. I'd say 70% interstate 30% in town.

The owners manual says to change fluid at 50k and 120k if you drive in extreme conditions.(then they list those conditions) Otherwise they say nothing about a service under non extreme conditions. I know the filter can't be replaced on these transmissions without pulling the trans and disassembling it to some extent so a service would just be a fluid change. Under normal conditions, should the fluid be changed or should it be left sealed?

From what I've found online is that when people are changing the fluid, they are just measuring exactly what they remove and putting that amount back in.

Also, the plugs are original. They are supposed to last 100k but I'd like to pull them out and have a look at them now.(probably should have done it sooner) What is a good brand to replace them with? Get them from Mopar or is a parts store replacement plug OK? Advance Auto lists Autolite/NKG/Denso and Champion. All say they are an Iridium plug. Thanks