The computer is usually not the problem. If your blower motor is operating on one speed only, you probably have a failed blower motor resistor. When replacing the resistor, be sure to check the wires because sometimes they will be overheated and melted and you will need a harness clip (pigtail) as well.
Do you mean that your radio is also not working. For that concern I will need some additional information. Does the radio have power? If it has power, when you turn it on, do you get nothing at all or static? Do the radio lights come on?
I'm not sure what you mean by the gas/mileage is on the computer. Are you getting poor gas mileage? Is your fuel gauge not working? I will need more specific details on that concern also.
Hi this is a different expert
It is possible the radio is causing your problem try unplugging the radio if the rest of the dashboard returns to normal the radio will have to be repaired or replaced (with a stock radio or CAN II compatible radio).
There could also be a problem with the other components that are acting up - the instrument cluster or the heater control panel or the body control module(computer for the body) but most times the radio is the cause.