If I received a corrected W2 from my employer and it only shows values in box 3 and 4, should I edit these boxes in my original W2 entry in Turbo Tax?

YES ... those are the boxes that changed so you will change only  them in the program. 

Got it thanks for the response. So I should still only have one W2 entry, but the boxes should reflect the corrected values provided in my W-2c?