To the Op. I believe it is a matter of respect to your Parents, yourself and your posessions to take care of what does not come easily.
Your crisis of measure is slightly unrealistic (I hope) dragging it across gravel etc. perhaps just a phrase.
The OtterBox Commuter is relatively inexpensive (Amazon approx. $22) it will protect the phone while maintaining approximately the same size and shape. It comes with a screen protector and it works well with no degradation of functionality.
An added bonus is the Commuter actually makes the buttons easier to actuate.
So, you will get a fair share of those who will tell you "Case, screen protector - don't bother". They however did not buy you the phone and I frankly doubt they will offer to replace your phone after the self-admitted inevitable "Drop".
Case - Yes
Screen cover- Yes
Piece of mind - Priceless