ERROR: syntax error at or near "select" at character 9

Hi

I am using PG 8.0 on Win32, learning SQL.
I dod create a table with the following SQL:

CREATE TABLE test (
id integer,
nev varchar(25),
datum timestamp
);

A sequence with:

CREATE SEQUENCE "public"."test_azon_seq"
INCREMENT 1 MINVALUE 101
MAXVALUE 9223372036854775807 START 101
CACHE 1
;

A before insert trigger:

CREATE FUNCTION test_verif() RETURNS trigger AS $test_verif$
BEGIN
NEW.id := select nextval('test_azon_seq');
NEW.nev := nev;
NEW.datum := current_timestamp;
RETURN NEW;
END;
$test_verif$ LANGUAGE plpgsql
;

CREATE TRIGGER test_verif BEFORE INSERT ON test
FOR EACH ROW EXECUTE PROCEDURE test_verif()
;

When I issue the

insert into "public"."test" (nev) values ('Graf László');

insert statement, it returns

"ERROR: syntax error at or near "select" at character 9".

Why? What is wrong?

--
László Graf