Thanks for your kind replies.
1) I have worked on PIC18F a year ago for a small project. But its my first time to use GSM module, therefor i will need to study (for the GSM-PIC interfacing) before i get my hands on the project. Material can be links/books which you people can kindly suggest (any) will be helpful.
2) Which PIC family/model should i choose for my task, I just have to use GSM and External alarm circuit to drive. How many pins will be reserved by the GSM module ?