If you click on the Search option above there are a number of guides for the P8P67 motherboard that should help you get things working.
I would suggest that work on the issues one at a time, keeping track of what you do, in case you need to back up. Just remember to always run System Utilities when you add or delete a kext.
You need to choose the appropriate kexts in MultiBeast for sound, networking full video functionality as well as self-booting. I suggest either following on of the guides for the P8P67. Most of them are for the PRO version, so you should check that the sound Codec and Ethernet chip sets are the same.