That's the generic question.
Edit: Currently machine is m1-small Ubuntu 64bit changing to m1-medium.
Here are some of the components on the box: -lighttpd (webserver) -fastcgi -django -gps tracking server (written in python) -.com.au domain -postgresql -postgis
Stackoverflow related How to change instance type
Edit: Upgrade went smoothly - no issues at all. Just took a snapshot of boot volume then changed the instance type after stopping the machine. I did as expected have to re-associate my public IP address back to the instance using Elastic IP(very easy) Before doing the upgrade I moved my postgresql cluster(data files) back to the boot volume (since it's small enough) as you can't snapshot instance drives.