How to unbrick my Moto G 1st Generation ?

I recently flashed 5.1 Lollipop on my Moto G, after that i went in recovery mode( by mistake) and tried to reflash it through the zip folder which contains the OTA file http://forum.xda-developers.com/moto...d-ota-t3192870
after some the screen displayed installation failed and my mobile went in fastboot mode. I tried to do factory reset and even wipe cache partition but now i am unable to start it. I went to service centre and they are telling to change motherboard.
I request to please provide solution to my problem. :(

replaced 3rd generation kdx7 with 4.5.3

Hey guys, just wanted to ask what would be the best route to unlock the bootloader if possible on my replacement hdx7 3rd gen? It has 4.5.3
I want it rooted and romed:D