By the way, here is the listing on GrabCAD. There are several file types to choose from. The one that seems to work best is the STL file.
So you've downloaded an STL, imported it as a part into SolidWorks and then add it to an assembly?
Regarding the scale: when you open an STL file (instead of dragging it into SW), there is an options menu where you can select the units of the original file. That list will probably contain the unit that the part was made in.
And then the assembly question. When you add the first part into an assembly, SolidWorks fixes the part in place. There should be '(f)' in front of the part in the tree. You can right click the part in the tree and select 'Float'. So you were actually really close regarding the nomenclature Now you can rotate the part and add mates to lock it into the right orientation.