Serial Enabled 16x2 LCD - How many pins ?

Yep,
Note that for the serial LCD you only need a TX line.
Use the HW serial for the GSM, and use software serial for the LCD and define pin -1 as the RX pin (yes minus one) of the SWSerial. This way you do not loose a pin.

(disclaimer: This trick works with the newsoftserial on which the 1.0 SWserial is based)