One of the "Bondi Blue" originals... 🙂 (Just to confirm, it is a greenish-blue color and not one of the "fruity" colors that came later. If you do an "About This Mac" from the Apple Menu on menu bar, it should say it's 233 MHz.)
If you want to find a business that repairs Macs (even old ones), you can use this web site
http://www.apple.com/buy/locator/service/
But the cost may be high compared to the value of the Mac at this point. Well, except for sentimental value...
That iMac is designed so that the entire "computing" portion is all on a "tray" inside the computer, that you can pull out and work on. The rest of the iMac (the non-computing portion) is the outer shell, display, speakers, power supply, etc. The two portions connect to each other inside the shell.
Here's a video on YouTube of someone taking it apart.
http://www.youtube.com/watch?v=Tk3LuEQt8gc
CDROM drive is right there, at the top of the tray that pulls out, easy to take off and replace.
If you don't feel comfortable doing it, maybe you know someone who is handy with a screwdriver. That's the only tool needed.
The replacement part is available from some places online. For examples
http://www.wegenermedia.com/imaccd.htm - For your iMac, it would be the part labeled iMac 24xCDROM Tray-loading drive. Fits early Rev1 tray loading iMacs (233mhz).
http://www.welovemacs.com/cr175d.html
eBay may have the part as well (just make sure you get the part that's for your iMac model).
Any replacement will no doubt be used or "refurbished" at this point.
