Default [Q] Re-install AT&T Software Update (OTA Update) App

I rooted my N900A with Root de la Vega and running MI1 but do not have the AT&T Software Update (OTA Update) app installed and don't have it backed up in tibu. Is there a way to reinstall the OTA Update? Would like to get the MJ5 since you can keep root. The Software update in device settings does not do anything when I press it. Thanks!

Just found out if I used Root de la Vega and somehow update to MJ5, I will brick my phone. Also, I tried downloading Kies 3 and it says "Your device's current firmware version is not supported to update firmware via Kies." Current firmware version: PDA:MI1 / PHONE:MI1 / CSC:MI1 (ATT)

Is it worth upgrading to MJ5? Any post on the benefits of the MJ5 update? I don't have any audio problems that I can hear.