By no means a simple task. Unfortunately the promise of computing design and the realities of it are two different things. In the extreme. Particularly when you throw in new objects and the need for lighting and shadow consistency to an existing image. It might be easier to start from scratch. But about your stated goal, first:
The best software to do this sort of thing takes the better part of a year to learn and requires that you come to understand many of the paradigms and problems of computing design.
3ds Max is the best for this, but you will need to use it in conjunction with image editing software like Photoshop and a compositor like After Effects in order to get the best results.
Even for a professional the task you describe is by no means trivial if the quality of output is to be vaguely considered a compelling image. If the image is required for sales materials then the effort required can be measured in multiple days, even for a professional, for one photo.
And professionals with these kinds of skills charge 100's of dollars an hour. That's USD.
Just matching shadows and lighting when removing objects is difficult. Doing it when adding objects is a whole other level of skill. There's probably less than 10,000 people in the world that can do that with any level of proficiency, and most of them are ably employed making TV commercials, print ads, movies, special effects and other such things in well paid, exhausting roles with incredible production deadlines.
To be able to do this yourself you'll have self educated to the point of being utterly employable. It's really that difficult to compose with shadows and correct lighting on new objects in an existing scene.
Unfortunately this task is sufficiently difficult and time consuming you have to think about the cost benefit ratio.
And, interestingly, there's another option:
Getting someone to recreate the room, from scratch, in 3D, and lighting it to their own desires, with the changes you desire. This is probably the cheaper and faster option. It won't be your photo, but you'll have a room that can now be rendered from any angle at very reasonable quality, with any number of additions and subtractions of contents.
To this end, if this is appealing to you, you can get started in Sketchup. You might even get a sufficient result yourself with that, but be prepared for a longish learning curve. Weeks, not days. It's clunky, but the easiest modelling paradigms for a newcomer to this sort of thing. See this time-lapse for inspiration: https://www.youtube.com/watch?v=Ho250LMTQbo
And not to be off-putting,but it is possible to take the primitive geometry of Sketchup drawings to this level:
BUT, this takes some degree of mastery of a thing called V-Ray. And you can probably safely add a full month of full time study and practice (I mean well more than 8 hour days) to learn the intricacies of render settings, lighting, shadows and finally materials... sufficiently to get the kinds of results you're seeing here.
And, believe it or not, I think that combination of Sketchup and V-Ray is probably your easiest and fastest path to what you want. 2 months. Minimum. Full time.