The biggest danger to Russia is Ukraine, they will not accept to give an inch of their country to Russia, the russians however could have some mwanya in that a good portion of ukrainians (them country folk) identify with russia for political reasons.
Aside from the Crimean Peninsula that is historically a Russian Naval facility similar to GUAM, Pearl Harbour, Diego Garcia or Okinawa for the US, Russia is not laying claim to any other region of Ukraine. Therefore, Putin is playing smart.
Contrary to opinions here, Putin already lost round one, in that the Ukranian leader ousted in the just concluded riots was russian leaning and the ukranians kicked him out coz he sided with Russia over the EU, so this new crisis is his second move.If this incident cools off at current status, the impression Putin will be creating is that he has gained, yet the fact is that nothing has changed, infact he has lost coz the Ukrainian leadership firmly shifts towards Europe. He has gained nothing he already had in the Crimean peninsula as it was already a Russian Naval base.
Putin and Russia will actually lose upto an entire decade of goodwill as a result of this crisis, because for a leader stability and reliability is extremely important.
China will certainly not support Russia, their strategic interest would not allow a Stronger country sharing with them over thousands of Border, plus a weakening of Russia works in their favour while a weaker US for now does not favour them.
"The purpose of bureaucracy is to compensate for incompetence and lack of discipline." James Collins