Case Insensitive & Accent Insensitive

Hello,

We have an application we want to migrate to PostGreSQL. Our application uses a lot of
queries comparing strings with Like and =. It is an application for libraries and we need to do
the comparisons in a case insensitive and accent insensitive way.
We are trying to save time. We have about 700 queries in our app we had to change if
we choose an option as using regular expresions or upper(). And these option does not
solve all the problems.
I would like to know if there is an easier way which does not involve to change the 700
queries. It could be, for example, to change the character set of the database.
Thank you very much,

Ícaro Alzuru C.