SQL Server trigger (update or insert with inner join problem)

Question

ALTER TRIGGER [dbo].[killertrigg]
   ON  [dbo].[tbl_pvporderview]
   AFTER UPDATE
AS 
IF (UPDATE([Kill]))
BEGIN
  SET NOCOUNT ON;

  INSERT  killer(serial,[Kill])
    SELECT i.serial,i.[Kill] FROM inserted AS i
    INNER JOIN deleted AS d
    ON i.serial = d.serial 
    AND i.[Kill] <> d.[Kill] AND i.[Kill] > 0;
END

However how would I go if I would want it to update if the serial already exist in the killer table. Could do update first and if it returns rowcount 0/null then do insert but I got stuck WHERE - since I can't use i.serial = d.serial to compare there.