Im currently running Gnome 2.16 and I think it's t...

Im currently running Gnome 2.16 and I think it's time to update to the latest version (2.20) I think. I would like to run " emerge world" but would like to make sure I have a working system after the update is done. Among other things, I need to upgrade to GCC 4.0, the latest gnome version, etc. What would be the best approach to ensure that my system is up to date with having to spend hours/days fixing anything that breaks during the update. Thanks in advance.
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Asus A8N-SLI Motherboard
AMD Dual Core X2 4200
XFX GF 6600 256MB PCI Express Card
250GB SATA Drive
1.5 GB PC2700 Ram
**Coming Soon another XFX GF 6600 256MB PCIE for dual video card
setup****