I do believe there will be a war on the mainland of Ukraine. Crimean peninsula is already gone for all intents and purposes. Currently it seems that most NATO countries (even Germany to some extent) are preparing Ukranians for guerilla type warfare. Historically one of the many reasons for the downfall of USSR was the fact that it got bogged down in Afganistan. It is not impossible that this in turn might be the downfall for Putins regime as well. Keep in mind that militarily Russia is mighty, but economically even individual European countries are stronger. So a protracted and costly guerilla war could exhaust Russia economically.

I believe that the impact of political stability will not be significant for the countries that don't want to get involved. At least it wasn't very impactful when Crimea got taken or when the war in Georgia happened. Of course there will be a whole lot of political rhetorics (Eastern European countries will vocally demand strong Anti-Russian actions, some Western European countries will debate wether this conflict is at all relevant to them, Germany does what Germany does, USA-s both parties accuse each other of not being tough enough). However I doubt that it will make a huge difference in the end.