What I do, and its probably not the best way, is to have 2 partitions for Linux, one is for 'current' and one for 'future'. I have a home partition for user data and when I change LInuxes I can use the user settings saved in /home for the other install.
In order to update, or change distributions I would just install a new distribution on its own partition, so download a CD of Ubuntu, fedora, suse, arch or whatever, install it to your spare partition and tell it where the /home partition is, Ubuntu imports user settings automatically. Then you can start using it! This is without interrupting your existing install, so if you have problems you can still search the forums for solutions!
I hope this is of some help for you, and best of luck finding a distro which suits you!