OLED or not I can 100% guarantee you it’s not the same part. Also, ANY part you get from anyone except apple is not OEM (and if it is, it is stolen). Apple does not sell original parts to third-parties.
Finally, having a third-party tamper with your phone will destroy its waterproofing (not that there are any parts for the XS going around at the moment, stolen OEM, reverse-engineered knockoffs or not)
Your options:
1) Send it in. Since it’s so new they might just give you a new one for the price of the replacement.
2) Try to purchase AppleCare+ and then send it in (i think your phone has to pass some remote diagnostics first, I don’t think a cracked screen makes it fail such diagnostics).
I wouldn’t say 2) is cheating the system because this is a loophole so large you could get a whale through it, Apple knows it and does it willingly. Plus they’re a trillion dollar corporation.