First what u need is a custom kernel that will give u custom recovery...
Check out dorimanx or philz (other options too)
U can download a tar file of kernel and flash it via odin in download mode (volume down +power+home button )
Now u have a custom kernel
Now u need a cyanogen mod rom.zip file and google app zip file..
I suggest u to use cm10.1.3 stable version based on android 4.2.2
Download and put the zip file in internal /external card
Reboot to recovery (shut off phone and press volume up +power +home button)
Now u r in recovery
Wipe dalvik cache
Go to mounts and storage in recovery
Now select install zip from card
Choose the cm rom zip and flash it
Now choose the google app zip and flash it
This is just a over view... do some study and watch some videos