best practices for fixing stored procedures already in production?

we still have a long way to go before we can have database applications in
production,
so we're really just trying to get educated on best practices.

our production environment will most likely be a single postgresql server
hosting 5-7
databases (not set in stone, however).

we know we have a choice to have business logic code execute or "hosted" at
the application layer or within the database engine itself via stored
procedures.

what happens if we need to fix stored procedures already in production? are
there pre- and post-production practices that we should educate ourselves
on to make it easier on us to handle such problems?

we are currently a team of 2 developers who will also be the acting
database administrators supporting about 40 "non-heavy" users.

we are a windows os shop.

if you can point us to some online articles or resources that we can read,
that would behelpful!

thanks for helping!