iPhone won't work after restoring it because of some dirt?

Hello everyone. I have an iPhone 4S iOS 7.0.4 (the latest one).

I went to an apple store and see if my greyed out wifi will work, but unfortunately they said it cannot be repaired, I need to replace my iPhone for a new one...

Anyway, I asked if restoring my iPhone could work, and the technician said that he wouldn't recommend restoring my iPhone, because there is some dirt or maybe a little rust in the plug connector, and because of this, after restoring my iPhone it wouldn't work anymore. ***? Charging my iPhone works, syncing through my computer also does.

Why would my iPhone stop working because some dirt in the plug connector? Is it possible? Or maybe the wanted me to replace it for a new one?

Please help, so I can restore it and see if I can use my wifi again.

Thanks.