Help upgrading from 4.1.2 to 4.4.2

Hey all. This is my situation. I have a GT-5110N wifi only tablet that I purchased 2 years ago in Canada. The motherboard recently crashed and the repair place put in a SIM enabled motherboard Model SGH-I467 with Android Jelly bean 4.1.2 I wan't to upgrade to 4.4.2 as I had with my previous motherboard. With extensive searching I found out that this is an AT&T tablet. I try to use the OTA update on the tablet but it says I have the latest version. The AT&T website says there was a OTA update to 4.4.2 in October 2014. I've called both AT&T and Samsung for help. No dice. What can I do?? I checked on sammobile and they only have the 4.1.2 version. However, the SGH-I467M through Telus contains 4.4.2 Can I download that?? I'm new to rooting etc. Do I need to unlock device?? Please help.

Thanks