Yes you have to be gentle but it's fairly simple if your used to repairing them. Just take the unlocked logicboard and and place it in the new shell. Most if the components will stay attached accept for the screen and battery pieces. Take a picture of how it was before u start to disassemble the phone. There's good vids on YouTube Look up replacing the imei in your iPhone vids.
No one wants to be straight forward. Yes .by replacing the Logic Board/(Motherboard) You can turn it into a new working device. If your worried about keeping your old content u should have and k ow your own icloud set up if not you'll risk locking it up again. Also you can build the phone from scratch outside the USA easily. Stateside you'll have to find retailers who'll resale the parts. A lot of places won't but there are some who will. There's a Market for building and repairing phones don't let the 1 percenters and mass consumers Know tho cause then it'll ruin it for tech junkies.. See ya good luck do it at your own skill set and be sure research first if you don't know how and if u have a apple product the instruction booklet gives you blue prints. And reae down and repair instructions. Have fun!