Here it goes.
1.1.1. Get GraphicsUpdate, unpack it with pacifist and fix cpuid with Marvin's AMD Utility
1.1.2. Manually copy all the updates to root.
or
1.2.1. Get GraphicsUpdate, get patches.zip from this thread. Unpack patches to root (/) and install GraphicsUpdate. For me this results in lockup after install, but if you can reboot - do that.
1.2.2. Boot with -s (single mode), mount root as noted on the screen.
1.2.3. cd /patches
1.2.4. ./patcher cpuid-graphics.txt

2. At this point you'd better boot into -s (or continue old session), remove extensions cache and reboot with -f -v
3. If you get a lockup - you have to reboot in -s again and fix PCI IDs in corresponding kexts by the means of nano, vim or any other console editor. Remove cache, rebuild, boot with -f -v
4. If you get black screen at this point - back to single mode and try playing with NVCAP (found in the Info.plist of NVinject). You can get some here: http://nvinject.free.fr/forums/viewtopic.php?t=19 (04000100 00000300 0c000000 00000007 00000000 works for me).