Do I have to replace entire Display Assembly?

Such screen assemblies should not be so expensive anymore and the sound you hear probably comes from the hinges and it wouldn't get fixed by replacing the glass only. Replacing glass only would take quite some time but is feasable with some patience and work time..if you have both, why not ? You'll have to remove the screen, use hot air and some plastic picks to remove glass without damaging the lcd panel, clean glue residues, apply biadhesive tape, keep everything very clean to avoid dust on screen when you close your new glass in place and then need to reapply some mild heat and pressure clamps to firm the glass in place.

After that you should examine the hinges to find out where the sound comes from and why and possibly have to replace them with new ones. Does the screen assembly option still sounds so expensive ? =;)