Schematic:

The circuit is powerd by a stabilized 5V VCC whose absorption depends mainly on the display backlight if used, otherwise the current should not exceed 100mA. The radio reception is handled by CCP1 module of the PIC, while the RF transmission stage is managed from the CCP2 peripheral that in this case will be set as PWM. For the radio transmission, I advice the use of anoff the shelf radio module, like Aurel or Mipot. Moreover take notice of the connection with RS232 driver for the interface with a PC (Hyperterminal for Windows or Minicom for Linux - click on the link if you want to read more -) and the connections to the 16x2 display in order to display the received code. The choice of the display is up to you, there are many types and I'm sure you already have one in your laboratory, therefore verify on the datasheet the pinout correspondence between the display and the connector.