You can replace broken ones with oem rear glass. You should be fine apple may not notice. You change it to a color glass, they will notice. You turn any screws on an apple product it does void your warranty. Buy, sell, ship in for repair.
Problem is that it's not seeding right not that the glass is to thick. I wouldn't buy parts off eBay. I used a place close to cincinnati they have a ship in service. Parts are high quality, fast shipping and super nice people.