the licensed clinical social worker told me that being in the psych ward is not a crime, so it does not show up on criminal background checks for work.
however, maybe for military background checks, police, firefighter, civil servant, etc, that might be different.
in any event, it would not hurt to apply for the peace corps. besides, the peace corps does not accept every application. if the peace corps takes you, great. if the peace corps rejects you, you can ask why.
however, the peace corps' website says that each assignment lasts 2 years 3 months anyways. so, even if you do join the peace corps, you have to find something to do. in terms of work. after you get out the peace corps.
likewise you can purchase your own rap sheet.