Vanilla power management is one of the main advantages of using a patched DSDT. The system will still work with NullCPUPM, but you won't have this benefit.
No, it's not normal to end up with errors. If the "fix errors" button doesn't fix them, copy/paste the messages here.
In my Asus N53JQ I use the SL_PS2_Voodoo.zip from this topic, but I have to remove VoodooPS2Trackpad from VoodooPS2Controller.kext/Contents/PlugIns so it works with the mouse plug-in.