It doesn't matter...
On new builds I've installed card first
On existing servers - the drivers are usually pre-loaded (from last time)

However - in your case - Id remove the card and follow instructions to remove driver
- reboot
- reset PRAM (allow to boot)
- shtdown
- re-install card
- boot up
- instal drivers
- reboot
- start NEW blank catalyst show
- enable LFG in preferences
(hopefully should work....)

The file is sent a link to above DEFINITELY works - its the one I use (almost) everyday!

Simon