need to replace a two foot by two foot area so can i get but one small square of sod?

Yes you can. It's $2 piece.

You would need 2. Don't let it dry out water it rveru day for 2 weeks

Yes Jefferson feed will definitely have what your looking for

Delta sod, Jefferson, and home depot all sell single pieces of sod measuring minimum 12" x 16" (the sizes vary a little but all cost the same) roughly $2 a piece