Nick if you look on the bottom of the foot your iMac stands on you will find a plastic plaque with the serial number and other information. The serial number can be used to find out which model you have.
If the hard-drive were under a recall or maintenance program the labor for replacing it...
If your backup is an exact copy of your main hard-drive then chances are pretty good that should your main hard-drive fail you can:
1. Replace the bad main hard-drive with one comparable to the one you have in it or BIGGER.
2. Boot your machine from your backup hard-drive. Most newer laptops...
The problem with MOST portable hard-drives that are made with a FireWire interface is the maker typically hobbles it with an external power supply.
For portability and compatibility I would go with a small hard-drive that draws all the power it needs from the USB port.
For graphics and...
You might also look into Drupal (drupal dot org).
I have used it in the past and I know it can allow for content that is invisible/visible depending on authorization.
There are also a ton of add-ons and modules that allow it to integrate with popular forums and photo galleries for example.
As a new enthusiast I was looking for the same kind of information. I thought I would share this:
http://cessnaflighttraining.kingschools.com/course/ppc/privatepilot.aspx
Not free, but could be well worth it. There is a very limited demo that's free to use, which I found pretty interesting.