Default [Q] i9300 mobile network issues :S

I'm having some issues with my i9300 i bought not too long ago pre-owned, i'm going to try my best to keep it clear and simple but...

I bought a i9300 off ebay locked to Optus mobile network, now before I tried to unlock it i rooted it and installed the cyanogen mod 10.2.0. Now I cant read my imei number and some other specs on the phone, i believe you need the imei or else it wont always work i'm told (unlocking the network). Ive been looking around for a stock rom from optus australian versions to see if that fixes the imei problem (didnt check to see if it was there when I had original rom on it). I've been running into problems finding a site that lets you download over 1 gig files without registering (**** that ****). Now I have two questions.
1. Can someone point me to a link of a fool proof no surveys and no registry restrictions of a stock rom from optus??

2. Is there it required to have an imei for unlocking or will unlocking fix my imei problem??
Is there a free way and relaviley easy way to unlock my phone??

Appreciate any help and ask for any more information

Additional imformation:
IMEI is Unknown
IMEI SV is Unknown
Serial No. Know
Have IMEI under battery