Oh, I was thinking about a laptop. They usually have that one single screw holding the optical drive in the slot. Now that I started thinking about it, I just opened a Vista based gaming laptop that had two screws securing the optical... And sometimes the screw is under the bottom service hatch. Anyhow, that's very straightforward to do unlike many other things inside a laptop. The drive just slides in like on rails and gets plugged into a set connector.
If it's a desktop built very tight, it can be more fiddly. The main issue would be to find and detach the cables without twisting anything.