this is your rom, or the closest thing I could find to it: http://forum.xda-developers.com/showpost.php?p=43459658
follow the instructions.
I googled your baseband number, which gave me the missing piece to the jigsaw, your version-main which is 3.62.1700.1
If a phone repair shop cant fix it, then the simple answer is, don't ever go back there for anything, he's useless.
1- he can pull p6 to get the original info about his phone, it's not necessarily a GPE edition
2- black or white bootloader could have been more accurate than just/only the radio+hboot combo, as he could have flashed the GPE radio only (very unlikely in this situation, but for future reference)
3- OP, do not even THINK about S-ON !!!