Q: G3 233Mhz DVD Upgrade?

This will be problematic.  It will be cheaper to buy a computer with a dvd drive already in it.  Like: iMac g3 400 dvd or iMac g4 dvd.

Apple used laptop cd-rom readers in the iMac g3's.

You may run Mac OS 10.3 on this machine.   Mac OS X takes about 4gig.  You can trim it down to 3gig with a custom install.

spec on iMac a and iMac b

http://www.everymac.com/systems/apple/imac/specs/imac_ab.html

This will require a minimum of 128meg of ram. More is better. I'd suggest 256. iMac g3 233 model a max memory is 384meg. I believe that the model b took 512meg of memory and ran at 233 [ I'm getting fuzzy on this. ] There are two memory slots. One must be Low Profile memory. Be sure you can return your memory cards. iMac memory cards are finicky.

http://eshop.macsales.com/shop/memory/iMac-G3-G4/

All the tray loading iMac g3's, models a-d, are constructed the same.

While this article deals with adding memory, you should see the pram battery on the logic board when you get to step 17.

http://docs.info.apple.com/article.html?artnum=43012

You should skip steps 17 to 20. Look for the pram battery instead.

http://docs.info.apple.com/article.html?artnum=43013

Here is a good disassembly page:

http://www.macopz.com/columns/imacrepair/disassembly.html

The second article in this series has information on replacing the battery:

http://discussions.apple.com/thread.jspa?messageID=2584291

How To Upgrade Your iMac

http://www.djonmac.com/

The tray loading iMac requires the boot partition to be within 8gig. Since there are hidden partitions before the first visible partition, people recommend that you make the first visible partition 7.5 gig to 7.9gig.  The machines support upto a 128gig Parallel ATA drive.

You should be able to use Unix symbolic links to 'move' some directory like /Users to the second visible partition.

Robert

R