I don't envy your task, but it's not impossible. Think in terms of building the chair. Maybe start with an extrusion of the general outline of the back (with cutouts), then "trim" away the edges with filet, like using a chisel. Add fine details by starting with one extrusion, then creating patterns along curves. For the legs, you could draw several cross-sections along the leg and a line following the centre of a leg and use a Swept Blend. Anything will take a fair number of measurements, but starting with the basic shapes and then trimming away step by step you'll see the chair emerge. Finally, for things like the cushions, you can apply different finishes in the render options (View > Color and Appearance - choose "Surfaces" under Assignment, and I think you can add to the System library, although I haven't done that myself). Good luck! Hope that helps.