The upgrade process wipes out the 9.10 installation unless you have lots of
hard drive space in which case you can have both 9.10 and 10.04. Just create
another partition and use grub to selection which one to boot.

In the installation process you should choose to format the root partition
because installing on top of the old installation can cause mega problems.
Even if you managed to do this successfully, your sources list would be for
lucid and not karmic and all of the old drivers and grub would be replaced.
I don't think that it would be a pretty picture.

The good news is that the new kernel includes more drivers and support for
devices. As for settings back them up to a usb stick and copy them back to
the new home folder.