basic cobra questions

[93GTDIN]

I just got my 1996 cobra coupe last week and i've got a couple of basic questions.
As of now the car seems to work great.

What are some common problems/ solutions I may encounter while owning the car?

Where on the temp gauge should I start worying about overheating. MIne stays below the halfway mark most of the time but sometimes gets as high as the "A" in normal. Is this okay?

What kind of gas mileage does everybody generaly get?

Does having the 2 O2 sensors instead of the four original ones effect gas mileage/driveability?


Also, are all speedo gears the same? IE if they work for a fox, is it the same gear for a T-45?


thanks

dino