Sounds like an interestign project. I have some experience setting up the MCU port and crossbar for UART applications. Do you have the data sheet for the particular MCU you are using? Do you plan to connect your MCU to a PC a review the data in a hyperterminal session?
void main()
{
initUART();
delay();
sendString("AT+CMGF=1"); // command to select text mode
sendChar(13);
delay();
sendString("AT+CMGS=\"0999999999\"");// here 09999999999 is recepient's number
sendChar(13);
delay();
sendString("Hello!"); // Hello! will be sent
sendChar(26);
sendChar(13);
}