Download update.zip from the guides. Place on internal storage of the phone. Not micro SD.
Download the ROM. Place on internal storage of the phone. Not micro SD.
Shut off phone, enter recovery mode. Click reinstall packages. It should reboot and look like nothing happened click reinstall packages. It will reboot into Clockwork Mod Recovery.
Wipe data/factory reset. Clear cache. Go to advanced, clear dalvik. Exit advanced. Click install zip from SD. Locate and click on the ROM .zip file. Let it do its magic. It should reboot normally, do the Google setup and put phone down and let it sit for at least 10 minutes. (Its still working in the background even though you can see nothing happening.)
If everything went well you should be good to go. If you have any questions, hit us up.
Tip: in Google type site: xda Samsung Vibrant cwm update.zip
That should get you to the proper thread.