How should it be on 1995 or in 1995?

First, stop driving it. Next determine why it is overheating. Check the radiator cap, and replace if necessary. Check the cooling fan and water pump for proper operation. If they are both good, then...

I get 34 MPG . I check each time I fill it up. About 60% of my Driving is on the freeway.

10 cents or less.

yes, it has been done many times, i currently have the 3.55 final neon tranny installed. stock is 3.50, the gearing is slightly taller in all gears as well.

depends how many miles. but 10W 30