Begin / End blocks

Howdy:

Running Postgres 7.1.3 on RedHat Linux 2.4.7-rel 10.

I'm trying to learn how to use the BEGIN / END
blocks.  My goal is to test the count
of a table and do such and such from there.

[pseudo code]

begin
        if
                select sum (*) from table < 1500
        then
                select into new_table * from table
        else
                return ''f'';
        end if;
end

[/code]

questions:

* Do I have to make this a function? 

* Is there a way to assign the value of
the count (or, sum of records in table)
to a variable and test for -that- ?

* I'm looking at the postgresql.org site
for examples, but all of the BEGIN / END
blocks are within creating a function - I'm
not sure I want to create one ...

* I'm sure the code above is wrong
(especially with the if statement) -
where can I find better code (groups.
google.com isn't working well, either).

Thanks!

-X