The 99% alcohol isopropyl "bath" worked. Either that or it was simply the tear down that jogged something free (or back together).
I just REMOVED THE BATTERY FIRST, unscrewed both the lower and upper IC boards, loosened all the ribbon cables so the lower IC board could be flipped up (not removed completely), unhooked the cable from the power/volume buttons (didn't remove the button assembly screws at all) and then gently washed the whole works with alcohol and a soft small bristle brush. Then blew it off VERY well but gently (let it dry dry dry...especiall
I left the upper IC attached (it seemed glued on there pretty well and I didn't want to force anything since this is my first tear down of a 3rd Gen).
Put it back together, DFU'd it, restored it, tested it and was VERY excited to find that both the WIFI and the Bluetooth areas are now both active and usable. I REALLY hope they stay that way for a long long time to come.
I'm facing this exact issue. I bought it "as is" on eBay water damaged and in need of a new LCD. The lcd is on now and looks sweet. All is well...but for... in the settings it shows a greyed out section for bluetooth and wifi. I did the restore a few times and still nothing.
In answer to your question I think the wifi, bluetooth and antennea for both are all connected to the logicboard and not replaceable as a separate unit. But I may be wrong.
I'm hoping that maybe some water/liquid might have crossed some connections and a good alcohol bath might fix the issue.