Conversion of dwf to skp, i.e. import of AutoCAD designs to SketchUp is possible directly through the File ► Import function, but in some versions may be only available to the Pro, a.k.a. commercial version of SketchUp.
You won't typically encounter any problems, however, make sure that same units are used in the DWG file and SketchUp to avoid scaling issues. Also be sure to explode all 2D polyline objects in the .dwg file, because arcs within a 2D Polyline will appear straight when imported into SketchUp unless you explode the 2D Polyline first, so the arc segments are extracted from the polyline.
Except for SketchUp, some 3rd party CAD/3D modeling conversion tools may also support SKP format and allow dwg to skp conversion.