I have done this with the 32 bit DVD. I did not keep my settings, but I did keep my home directory, i.e all my media files. However, if "settings" means database entries for the system, keeping them should be a simple thing. And then the 32 bit DVD will just replace the OS. I am not sure how it will affect MD's as I always re-created them, but your media will stay in tact.
I can only guess what "settings" is, but if it is just db entries, they should just be re-imported into the new db.
A side note. If you use the USB-UIRT, you will need the x86 fix from the wiki if you do not use IR dongles, and wish to have it blast "stand-alone"
Best of luck to you.
Perhaps someone who is more versed on what "settings" is can chime in as to how they are saved/imported.