Hi,
the gears will switch up to the 4th in S. Just wait while going at least 100km/h or accelerate upto more than 180. Otherwise there's a problem.
Osscillating accelleration can be a symptom of a faulty lambda sensor. Just get it replaced. This thing doesn't live longer that 50000km. You can check the momentary fuel consumtion, too. If it jumps +/- 2 litre while going steady then it is the lambda for sure.
If your trip computer worked without any radio then check your wiring. Maybe one is connected wrong or you cut one while installing the radio.
Good luck
Michael