MacBook Pro 13" wont connect to wifi My Macbook Pro was broken and I had to fix it at a Apple support.  

Afterwards, I noticed that the wifi symbol is not showing up on top of the upper task bar.
I opened system preferences and went to network, &amp; noticed that the wifi and the bluetooth tab is gone, it shows only ethernet and firewire, so I set a service order and no wifi tab pops up, only the ethernet tab and the firewire tab.
At the lower left corner of the Network page in System preference, there's a "+" button. 
If you click it, you will have a drop-down window asking you how you'd like to create a new network service.
From there you should be able to select "Wi-Fi" as its interface, and give that service a name.
Then click "create", and you should have the "Wi-Fi" tab back.
Then in the Wi-Fi tab, at the bottom there's checkbox "Show Wi-Fi status in menu bar", check it and the Wi-Fi symbol will be in the menubar.


After all these steps you should be able to connect to Wi-Fi networks just as you usually do.