You can finish this task with a controller having only 1 UART module.
what you need to do is to connect the PIC “RX” to GPS module and connect the “TX” of PIC to GSM modem.
Continuesly read the value from GPS and filter the values which you require.
Next you send the command AT+CMGS= after that send ASCII of “ENTER” ie,0x0d.
now wait for few millisec.
send your value got from GPS modem.
SEND the ASCII of “CTRL+Z” ie 0x1a.
Now repeat the same again after few secondsss……….