For anyone that replaces both lower dock connector and the black speaker/mic box. If you have no service or searching for network then the black speaker/mic/radio connector is the culprit! ask the vendor or person you got it from for a replacement!
I just spent an hour figuring out why my friends iphone wouldn't work after we replaced these 2 parts.
I ended up putting in my iphone 4 black speaker/mic/radio into this iphone and it worked!!!!