For "Salaries and Wages" in TurboTax Business, do I enter gross or net amount?

You report the gross amount.

Thanks.  In this case, does the gross include the amount that the employee deducted for 401k contribution?  (Note that I'm not talking about the amount that the company is matching, if any)

Yes, the gross amounts must include employee salary deferrals to the 401(k). They should the sum of the amounts reported on box 5 of your employees' W-2s.
If you have any further question, please add a comment. Hope this helps.

Ok, I'm not sure what you mean by summing the amounts in box 5(medicare?).  So just to make sure I'm reading this correctly, I'll give an example. If salary is 60k and employee contributed 7k to 401k, I should still enter 60k?

Yes, you are correct.