Ps3 slim blu ray laser replacement

OK so i used the video posted to here from consolezombie to replace my blu ray lens. disassembly was great no problems at all. my problems began with reassembly. while it should be easy enough to just reverse the steps, i had a group of different problems when attempting. I cannot insert discs now due to a white piece of plastic which is on a spring on the bottom black plastic piece of the drive. it blocks the discs from going in. i once accidentally had it down, reassembled it all, and then my ps3 wouldnt register the disc, then wouldnt eject it, and then when i manually took the disc out, the plastic piece went back to where it was. if anybody can post or find a detailed reassmbly video or manual for the ps3 slim blu ray drive, i would very much appreciate it