Nick, Lightroom offers local adjustments, but perhaps not in the way you are thinking.
Yes you can change the colour of a sofa. by painting over the sofa with an adjustment.
Yes you can 'rub an area out' if you mean using the clone brush or spot healing brush.
THe area you can select for the clone or spot tool is circular only. Therefore, you cannot make a selection of the sofa, delete it and swap it for another sofa.
Lightroom is not really designed to handle photo manipulation, more photo tweaking, and as a hub of your workflow.
Is it worth it? I couldnt work without it...