2006 Suzuki Forenza spark plugs

I changed my sparkplugs today and when I started it up it had a rattling noise and white smoked for about a minute.what can cause this? When sparkplugs were changed there was oil in the spots where sparkplugs go. Also we know the gasket for motor needs to be replaced, but I don't feel likausee that would make it smoke because it was not smoking before I changed them