My Chev Suburban 1500 4WD diagnosed leak from oil pan and rear main seal.

5.3 i guess, when replacing rear main seal it will be easier to pull the oil pan due to the fact the transmission and flywheel will be removed to access seal! So i guess both need to be done at the same time.

yes but problem is i believe your rear main seal is a one piece lip seal and in this case the transmission has to be removed in order to replace.