If you are doing more parts replacement (e.g. memory) you can make more room by removing the power supply with the four screws that secure it to the back of the case. (be sure to support it as you take the last screw out, right?)

If your're done, replace the drive assembly and reconnect the cables (don't forget the audio cables to the CD drives!)

Secure the three screws that hold the assembly to the front of the case.

Slide the case cover onto the side with the thumbscrews and replace the gray transparent bezel.

Post an article on iFixit next time you run into something pointlessly complicated like this so you can save a poor guy like me a lot of time when Google comes up empty.