Hey so i'm still new to android, apple.... old habits die hard... but whatever so I just got the galaxy nexus and im stuck on stock 4.02.... and i want to get to 4.03........ unlike our friend here..... every rom i can fin for ics is on 4.03, not 4.02, what do I do?
Generalizing steps here but....
1 - Unlock bootloader
2 - Install a custom recovery
3 - Pick a 4.0.3 ROM you want to try out and download it. You can download it straight from your phone, or use a PC then transfer it to your phone. Make sure you grab the GApps if the ROM you choose requires them.
4 - Boot into your custom recovery.
5 - Make a backup
6 - Wipe. You will need to do this when changing ROMs, this wipes data and cache. Everything on your virtual sdcard will remain untouched (backups, music, videos, pictures...) Apps will go away though. You can back them up with something like titanium backup.
7 - Install ROM. Also install GApps if the ROM requires it.
8 - Boot into Android.
I, or someone on these forums if I am not around, can assist you with any step you need help with but there are tons of videos, guides, etc floating around this forum and the internet. I recommend you read around and get a little bit more versed into what you will be doing, prior to doing it. Not that the process is overly difficult, it is just my recommendation.