Mileage can be altered or a different cluster installed. Are you asking to have it "fixed"? ( if so, bad idea )

The trans was in the range of needing replacement, 97 used a bushing in between the front and rear input shafts. This wears and allows thrust washers to fall out into the planetary gears.

The typical head gasket leak is oil and not fatal. The front timing cover ( the width of the head / 6" tall ) can be a leak point too.

The engine should not smell rich when cold. Pull the fuel pressure regulator vacuum hose and look for raw fuel.

Where are you getting the 85C from? With the engine running and HVAC turned on, press and hold REST until the display changes to 01 / some value. use the + of the fan speed to scroll to 05 ( I think ) this will be engine temperature.