Hitler wanted to get Spain to come in on the side of the Axis but Canaris talked Franco out of getting involved he also dissuaded Hitler of pursuing it further by pointing out to him that Spain at the time was a very backward country and to embroil them in the war would produce an ally that was militarily insignificant whilst also burdenning them with millions more people to feed.
THere were no raids launched on Gibraltar by land that I'm aware of.
There was a plan, called Operation Felix, but nothing came of it. Can't provide a link as my PC has slowed to a crawl, but you should be able to find details on Wikipedia.