Replace logic board for iPhone 6... Replace the home button too?

Hello:

I have an iPhone 6 in very good condition… Except that it just stopped working a few months ago. It seems to turn on (the screen appears slightly less black than normal), and I can get iTunes to recognise it. However, it won’t sync or accept any updates to the software. I receive an error 9 with iTunes.

Apple “geniuses” have diagnosed this as a problem with the logic board, which of course they won’t repair, only offer a replacement phone (for an exorbitant fee).

I am thinking of buying a broken iPhone from eBay (one with a cracked screen), and using that phone’s logic board in mine, following the iFixit replacement guide.

I was wondering whether I would also need to replace the home button of my existing phone too, since I read somewhere that the two are linked, else touch ID won’t work.

Thanks for any helpful ideas and suggestions!

Mark