how do the pro's do this? (still a newbie)

Hello.
As a newbie in the stored procedure programming area I would like to know how
you could do the following with a function in plpgsql.
(It's a theoretical question, so do not suggest changing the tables :-)
I have

table A :
id integer primary key default nextval('something'),
dohA integer

table B:
rid integer references A,
dohB integer

and I wish to create a function "foo( dohA, dohB)" that inserts the values
dohA and dohB into the proper tables A and B and the reference in table B
should of course be connected to the PK in table A. You understand what I
mean, right?

Now, how do I write

function foo(integer, integer)
begin work
... please fill this space with some code.... !!!!
commit

Is there some realy good tutorial on this, please tell me so?
TIA, Gunnar.