Dear Seyong,
1. I think either method would give similar results because, as described in SAM's Help system, SAM uses the wind shear coefficient on the turbine page with the Wind Power Law to calculate the wind speed at different hub heights. SAM limits the difference between the measurement height and hub height to 35 m. If you want to use 50 m wind speed data with hub heights above 85 m, then you can use the method you describe, as long as you are aware of the limitations of the Wind Power Law.
2. I am not aware of a method for estimating wind direction data from data measured at different heights.
Here are links to a couple of NREL publications on wind resource assessment:
Clifton, A. et al. (2016).
Wind Plant Preconstruction Energy Estimates: Current Practice and Opportunities
. NREL/TP-5000-64735.
Olsen, T. et al. (2015). Small Wind Site Assessment
Guidelines. NREL/TP-5000-63696.
Best regards,
Paul.