Default i9305 with a i9300 lcd, imei Null

ok i bought a i9305 phone off ebay that had a cracked lcd, thinking that i could easily just fit my spare i9300 screen onto it and use away, but now i have been faced with the imei Null/Null and also the baseband is unknown on the phone.

messaged the seller and he says that it was his girlfriends phone and that he reckons its saying this because the screen isn't the same, can any1 else verify this for me?

the mobile looks legit like it came with the original i9305 lcd with the sticker on the back and also it matches the imei on the box that came with the phone so i dont think he is trying to do the dirt on me.

Just want to know has anyone been successful with just putting a i9300 screen onto an i9305 phone? i have seen only 1 post on google on some forum of only 1 person saying this happend them and had comments saying it didnt matter