The purpose of a question may vary. Some questions are a genuine request for information others are veiled statements. You question is half a question and half a statement. The gist of your question sounds like this: Do you agree that a person who lies is a liar? Of course, everyone would agree that a lying person is a liar. It’s a very simple question. So, I suppose, that your question is just another way to pronounce Russia a liar. And you are absolutely right that Russia is a liar in terms of the interpretations of the facts presented in your question. But would you consider it a lie if you deceived a killer which was going to kill your family? I doubt that. You would justify your lie by a higher motive. The truth is that everyone lies to some extent. The USA was lying about WMD in Iraq.
This is what Bush said:
There's no question that the leader of Iraq is an evil man. After all, he gassed his own people. We know he's been developing weapons of mass destruction. … And so we're watching him very carefully. We're watching him carefully," Bush said in an Oct. 11, 2001, address.
Now we know, he was lying.
You can read more about it here http://thinkprogress.org/security/2013/07/24/2117351/george-bush-wmd/
You are asking whether anyone more or less likely to believe Russia now? Well, the USA was lying and might be lying now. Did it hamper other countries to believe the USA? Whose lie is bigger? Who is the worse liar of the two of them? Trust to a certain country is not always driven by the presence of a pure conscience of the country you are about to partner with. It’s about your personal interests. Why does the EU support the USA in spite of the fact that the Bush administration was lying about Iraq? Because they gain some benefits from it, notwithstanding the lie of Bush. Politics is a dirty thing. The more you delve into it the more you understand that combining a pure conscience with politics always fails.
I also need to point out some points in your question which you present as facts while they are not so univocally accepted. These misconceptions lead you astray from the truth.
First of all, “change in government of Ukraine” is not the right way to classify what really happened. It wasn’t just a change but it was an armed uprising against the democratically elected President (V. Yanykovich). The next point is that to say “Russia seized and annexed the region” is not exactly right in this case. The absolute majority of the Crimean people voted for secession from the Ukraine and re-union with Russia. I, personally, voted for re-union with Russia and can tell you that nobody forced anybody to vote for something they didn’t want to. Everything was transparent, honest and liberal. Think of Kosovo for example and ask them who cut it off Serbia without even a referendum why they didn’t have a referendum and see who is a real liar.
Here is a good article by Neil Clark, where he raises good rhetorical questions about the matter of the truth and a lie in terms of recent events in Ukraine
http://www.infowars.com/im-confused-can-anyone-help-me/
So, the main point is what you want to do by means of lying or telling the truth. If you think that he who tells the truth all the time is a good man then I’ll put an end to such a thinking of yours. Here is an example from the New Testament where Pharisees wanted to stone a woman taken in adultery. Were they telling the truth? Of course. Did NATO approve their attack on this woman? Of course. Did the EU with the USA admit that this woman was guilty and deserved death in a strict accordance with the law? Yes!!!! But the problem is that the real intention of that crowd was not to follow the truth but to use the truth for bloodshed and discredit Jesus. By the way, Jesus was a liar in their eyes.
http://en.wikipedia.org/wiki/Jesus_and_the_woman_taken_in_adultery
But Jesus saved her from death and his intentions were higher than a formal truth. That is how I see actions of Russia in the Crimea. Russia acted like Jesus.
Here is one more website with videos, pictures and articles about the situation in the Ukraine.
http://ukr-news-spot.at.ua/