I expect that the Russians will occupy Crimea, and it will receive a government favored by the Russians and supported by much of the population. It may be annexed by the Russians, but I don't think immediately.

The Ukrainian forces will not fight; it is obvious who would be the loser. They will receive verbal support from the EU and NATO but no military aid.

Rather useless sanctions may be applied against Russia.
If you like Russian vodka, stock up; the U. S. and Canada may ban it as part of sanctions.