Any SQL-functions examples available

Hello,

I tried to write my first SQL-functions with the intention to
port some stored procedures from MS SQL server. It would make my
task much simpler if someone could point me to some simple
examples which demonstate the use of function parameters in
SELECT/INSERT statements and how to get the results transformed
into reasonable return types, for instance if SELECT was successful
return true else false, etc.

Thanks for any halp to a bloody PostgreSQL-beginner like me

Andreas.