Upgrading linux base distribution?

[ivanatora]

Hello,
I see there are various linux base systems (for linux emulation) available. Current installed is

linux_base-fc-4_13  Base set of packages needed in Linux mode (for i386/amd64)

I'm willing to upgrade, since there are more up to date systems like Fedora 8 package - linux_base-f8. I'm thinking of upgrade becouse some linux software doesn't work well:
1) Flash player for browsers doesn't work at all
2) Google earth renders graphics very slow

The question is how exactly to replace the package. Just remove the old one and install the new one?
I'm running i386 platform. Also I've heared that applications from ports are build against the default linux base system and I may have problems trying to install them on another base system. Is it critical?