Quotes and spaces

Hi,
I looked through PL/pgSQL tutorial, but I can't get quotes and spaces to
work in queries executed from Pl/pgSQl. Here is an example:

create procedure get_name(varchar)
...
BEGIN
query := ''SELECT first_name || '''' '''' || last_name FROM user'';
EXECUTE query;
...
END;
...

Basically I want to get full name, i.e. first name separated with space from
the last name. If I follow the PL/pgSQL manual as shown above, I get parse
error.
What am I doing wrong?
thanks,

Oleg