Gsm based home security system

Hi Friends,

I am very much interested in doing project with Microcontroller(AVR-ATMEGA 16). However i am new to this field.So i dont know very much in detail about programming part.However with the help of google i purchased AVR programmer and SIM 300 GSM module.

I want to do GSM BASED HOME SECURITY SYSTEM.It should have the following option.

1)The system should be made of Atmega Micro controller-ATMEGA 16(As i heard it is more simple to program compared to other and also cheap)
2)The micronctroller should be linked to GSM
3)There should be LCD DISPLAY .
4) I should be able to store min 10 mobile numbers
5)The mobile number i should be able to enter/change using press
buttons.To change mobile number the system should be secured by
password.
6)It is enough if i have one NC or NO contact where i can connect my
triggering magnetic door switch.

When the door switch is triggered the system should dial 10 numbers
one by one with a gap of approx 1mint. The dialing should stop if any
one mobile number accepts the call.

I tried lot in google to find the C code but couldnot get.Can anyone please proved me the C code for the above Or similar project.