If points \( A(3, -1, 2) \), \( B(6, -3, 6) \), \( C(4, -3, 1) \) and \( D(1, -1, -3) \) are vertices of a quadrilateral ABCD, write the position vectors of A, B, C and D and show that ABCD represents a parallelogram. Also, find the area of the parallelogram ABCD.