3GS ios 6.0 where to start?

[MoJ80]

You'll have to forgive me....I'm very much out of the loop.

I have a formerly used 3GS with ios 6.0 installed. It's not activated but still lists AT&T as the carrier. It's no longer used as a phone...just wifi only. Using the jailbreak guide on here (nice btw) it looks like 3GS/6.0 is not supported. So, where do I start? I assume I need to downgrade in order to perform a jailbreak? Also, the selector guide gives teh option of either choosing a carrier or wifi only. In my case the phone still lists AT&T as the carrier but is not activated and works solely on wifi. Which option would I choose?

Thanks in advance. My initial goal is to be able to access a bluetooth obd-ii reader for vehicle diagnostics but apparently apple does not support unless you perform a jailbreak.

Mo

[Simon]

If you want to downgrade first step is to figure out what shsh you have. Download tiny umbrella, click advanced and select request shsh from cydia. Then click save shsh and see what you get.