Q: Is there any way to be able to re-download iOS 6?

My device has been down since September 19th.  I need to know if there is a way to get iTunes to retrieve the download and reinstall it on my now truly unlocked but non-functioning unit.

Or how can I tell if my phone was adapted by the process which is not to be named here, and whether said unnamed process damaged files?  Is there any way to flash the phone or otherwise fix files that may have been corrupted by the process which is forbidden to be named here?

By the way, I am getting the "no sim card installed" message.

Any constructive advice and/or lessons learned is appreciated.  I thank you in advance.