The tried and true old 555 timer (LM555, NE555, etc.) will do the job for you, and if you're just starting out, they're very useful to learn. Best advice, start with the
datasheet and give it a good read and try to emulate the circuits shown therein; that should get you quite close to what you want.
For adjusting the frequency, you vary the value of the capacitor and one of the resistors. The duty cycle can be adjusted via the ratio between the two resistors. Once you've banged out a simple prototype, you can use digital potentiometers ("pots") to vary the resistance values via your display. (Or just use trimmer pots and keep it analog, if you prefer.) Hope this helps.