It is possible for a permanent resident to petition their spouse for a green card. Keep in mind that in order to obtain a GC through a PR spouse, you must wait for a visa to become available. The wait time depends on which country the intending immigrant is from.

The likelihood of being approved differs from case to case, and it depends on how the intending immigrant entered the US, if he/she has been deported (or deportation orders)/voluntary departure, if he/she has a criminal record, etc. It has nothing to do with whether the petitioner is a USC or simply a permanent resident.

If you are denied, I believe you can appeal the decision, but check with a lawyer to make sure.