Postgres UPGRADE from 9.2 to 9.4

I'll be migrating my Postgres 9.2 database from Rackspace to Amazon.

To do that work, I'll be using DMS at amazon... unfortunately DMS needs a Postgres 9.4+ version at least (http://docs.aws.amazon.com/pt_br/dms/latest/userguide/CHAP_Introduction.Sources.html) - So that means that I'll have to upgrade my postgres version.

Questions:

1 - I'll have to upgrade the version on my Master server, right? I can't upgrade only in a streaming replication slave server, right?

2 - I've never done a Postgres upgrade before, can you give some guide here? Is usually a easy thing? How long can it take? Is a downtime needed?

Thanks guys,

Patrick