Is there a way to upgrade to Ubuntu 9.10 without having to download and use an ISO image?
it's really non-geek if you follow the instructions to the letter. Fire up Terminal, and type the following line :
sudo apt-get dist-upgrade
There's a way with Synaptics, but trust me, this is waaaay easier.
EDIT : Missed out that OP wanted to upgrade to 9.10, which hasn't been released yet.
Do the above pre-edit answer first to upgrade to 9.04 (just to be safe). Then :
Type in Terminal
Update Manager should open up and tell you: New distribution release '9.10' is available. Click Upgrade and follow the on-screen instructions.