First the frame of S5 is plastic but not metal.
And then it's possible to replace it.
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But you will need a complete midframe such as http://www.witrigs.com/oem-midframe-assembly-for-samsung-galaxy-s5-sm-g900f-charcoal-black with some small components like headphone jack, earpiece, power button, volume button and loudspeaker, because they are difficult to remove and easy to break.
What else, you will need a piece of new LCD screen adhesive when assembly the phone such as http://www.witrigs.com/oem-front-screen-adhesive-for-samsung-galaxy-s5