date comparision

Is anyone out here can give some advice?

i have a table with a timestamp field.
i should know if there is records for the particular year and month
so i need a query like (in MySQL it was very simple, but i should move to
postgres!):

SELECT something FROM mytable WHERE MONTH('timestamp_field')=07              AND YEAR('timestamp_field')=2000 LIMIT 1;

So, i am looking for date/time functions:

SELECT * FROM table WHERE date_part('year',timestamp 'timestamp_field') =
2000;

but it doesn't work...(ERROR:  Bad abstime external representation
'timestamp_field')
may be i need subselect or abstime(timestamp) function??

I suppose it's a lame q, but i cannot solve it today...
Thanks!