Could Israel do a land invasion and occupy Iran if they had to?

The likelihood of that happening is zero. Logistics dictate that supplying a force capable of accomplishing that would be beyond the capability of any country bar that of the United States and even then only if America was not engaged elsewhere. The only military option that Israel has open to it is a sustained air attack concentrated on Iran's nuclear installations and even that would be a strain. Israel's best option is to work on anti-missile missiles and ready itself for a retaliation.