To change the look of a room it's simple - paint. Check out a how-to book from the library or online. When painting small areas, check paint stores for returned custom color paints. They’ll often sell them at a great discount.
If your sofa is in good structural condition, but the look just needs updating, use slipcovers to add a new look to conceal the flaws. And if you're in need of a furniture update try sanding the piece down and adding some new paint and/or hardware. And if you're feeling brave you could even try stenciling a snazzy design.