Ukrainian people love their freedom but have absolutely no military power to defend from the manipulative power known as Russia. Also they will be getting no help from the U.S for two reasons, One is that Obama is spineless and will probably draw the same red line that he used in Syria, and two Russia is willing to do almost anything, like putting in a puppet president, to get Ukraine to NOT join the E.U or NATO.
East Ukraine supports Russian rule and would welcome Russian troops as liberators. Russia will never let Ukraine side with the West (EU/NATO). They would rather invade Ukraine and set up their own pro-Russian Government then ever let it become a EU/NATO country. It would also give them a land route to the already annexed Crimea region. Also, no one wants a no go to war with Russia. The US and NATO may bully small inferior counties like Iraq and Afghanistan, but would never go the war with a superpower like Russia unless outright attacked on there home soil. This isn't 1914. If Ukraine joins the EU before they invade it might be a different story because then it might cause a war between the EU and Russia. Putin has a high favorability rating (unlike Obama) and a war against the west would gain him more support as a strong leader.
Yes, Russia will invade Ukraine, because they have given every indication that they intend to invade. Russia is already right on the border. They have already overtaken Crimea, because of its energy resources, and Ukraine is next. Ukraine is the next step to Putin reclaiming the USSR that he never thought Russia should have lost.
I do not believe it is question given that Russian troops have been in Ukraine for well over a week. I do not believe Russia is interested in taking all of Ukraine unless they can do it through peace. I think they are mostly guarding their interests, as a country.
The Russian Federation has already democratically acquired Crimea. Why risk an international uproar when you can simply have a democratic vote? The citizens in Ukraine are largely pro-Russia, so I don't think it'd be very difficult for Russia to acquire them in that way. However, the new government in Ukraine cares nothing for the people, so there is the possibility that the citizens of Ukraine may call for foreign aid, likely from Russia. Only time will tell.
No, Russia will not invade the Ukraine. Invading the Ukraine would be a very bold move on Russia's part. Russia would not be able to invade Ukraine without attracting a lot of global attention and creating more problems for the country of Russia. The risk versus gain would be too great.
Now that Russia has Crimea, I don't believe they will push farther into the Ukraine. Official elections will be held there around June, and until then, they may try to persuade voters. There is no real incentive for them to invade the remainder of the country, as it wouldn't look good for them in the upcoming polls. With the Europe and American strongly supporting the Ukrainians hope to join the EU, Putin understands that invading the rest of the Ukraine now, would only cause unneeded hassle for him.