Can a phone with a bad ESN be used for parts?

[Michtifus]

Hi y'all. Ever drop your phone in the toilet! Well i. Did a few days ago. It worked afterward and didn't seem like any water got past the case of it so I thought maybe I'd dodged a bullet. But I was wrong! It lasted about an hour or two - just long enough to sync everything and then it was blank.
I called metro only to find out that I no longer had insurance on my phone! So now I have to buy one. I loved my stylo 3 plus but cant afford a new one. I've noticed some for sale on ebay that say "Bad Esn for parts only" and another that says it is in good working condition and unlocked but the sim card tray is missing.

So the question is... (1) How hard is it to replace a sim card tray?
And, (2) which parts on a phone with a bad esn CANNOT be used and what are the odds that a phone like that can be combined with a phone like mine to make a good, clean, working phone?

 

[Jfalls63]

Sim card tray is easy. Pops out with tray tool or paper clip. Remove from old phone and insert in new phone. Needs to be same model phone.

ESN is assigned to chips on the motherboard and not legally changed. All other parts should be clear