Apple iMac Harddrive Replacement

Needed to replace the Harddrive on an Apple iMac. This is a white plastic Intel iMac. After removing all screws from the bottom (where the memory modules are also installed), the back of the case can be pulled off, starting at the bottom, with a 'crack'. There's a lot of aluminium-backed tape inside, and after removing the LCD panel the hard drive becomes accessible.

The original drive was 160GB. A 250GB replacement was found for around $60 (3.5", SATA).

Then it came to re-installing the operating system from DVDs, where I ran into two surprises:

1. No disk found.
   With Linux, installing an OS from DVDs is fairly straight forward. You are guided through partitioning the hard drive etc. With OS X, I was expecting it to be even easier, but wrong: The installation asks you to select a hard drive for the installation without offering anything. Solution: Close the installer, select Tools/Disk Utility from the menu to format and partition the drive. When installing again, you can now select the drive.
2. Can't eject the disk??
   When prompted to insert the second installation DVD, I could not figure out how to eject the first one. Nothing worked. Finally I learned that the drive was empty ... I had not fully re-assembled the case because I first wanted to check if everything "worked". When the iMac ejects a DVD, it's usually kept half-way in the drive because of the felt lining of the DVD slot. This time, the iMac had ejected the first OS installation DVD, it had rolled of the table and vanished under some cubboard. From the outside, I could not tell if there's a DVD in the drive or not. Since I didn't remember ejecting the DVD nor saw one in the usual half-out-of-the-drive position, I had assumed that it's still "in"....