im also a noob, but i got a custom rom working on my shv-e120L from stock jb 4.1.2
This is how i did it (found out by trial and error, so it my be wrong).
1. download stock rom ROM 4.1.2 E120LKLJMA4 from this thread http://forum.xda-developers.com/showthread.php?t=2354177 (thx Mr0lala)
2. flash...