Well replacing parts is fine on a Blu ray that has Original Logic board assigned to that PS3. Once the logic board is replaced or the whole drive, then you must remarry the Blu ray drive.
So maybe I am wrong but it sounds like that is what you need to do or make sure it has the Original Logic board.
You need to be on 3.55 CFW for the process of Remarrying the Blu ray drive - http://www.ps3news.com/forums/ps3-ha...-118548-5.html
So its either that is the issue, or you got a faulty lens replacement, which probably can happen. Because you can insert disk, eject disk fine, The loading wheel is present in upper right corner on XMB. So one must think it is the lens that is faulty.