My employer included my retirement in my salary and say they have changed it, but have not given me a w2c. Should I file an extension?

It is not necessary to file an extension unless you have a tax due amount in your return. They do need to change the W2 and issue you a 1099R for the retirement distribution.  This won't impact the dollar amounts in your return but changes the way your income should be recorded.

You can file the return as is now and then file an amendment once you receive the proper forms.