I don't think Russia wants to invade Ukraine, I just think they want to dismantle the millitary hardware that is close to their border. They took the Crimea peninsula from Ukraine but that is different because the majority of the people living in Crimea spoke Russian and wanted to be part of Russia. Most people that live in the Ukraine main land would never except Russian rule and there would be constant resistance from them. I think the Russians know that.
Right now it could spill out into a full scale war, both nations are at loggerheads.