Most my doors were already here, but I did have one moved over, about 6 inches. However, the entire space was demo'd, and rebuilt, so that's not the best example to draw from. If you want the door hidden, in a pocket, yes, you will need a skilled carpenter. Essentially, the opening header and frame, will become twice it's size, with the "pocket" part, hidden behind the wall. The studs/supports will need to be removed to make a space for the door to slide into. Do you have any switches or outlets on the fireplace wall?

How do you decorate your place, what kind of style, colors, and feelings? That will greatly influence the type of door you might want. Also, think of your budget, and whether you want to install it yourself or hire a professional (you don't need to tell us, just keep that in mind). Then look around Houzz, in the products page, they have lots of interior sliding doors and hinged ones, from elegant frosted glass in a dark wood frame, to rustic reclaimed wood planks. You may not want to purchase that exact model, but it might give you a better idea of what would fulfill your airflow needs without sacrificing style.

First of all the images you posted you cant make anything out what you got there. Secondly you should contact a local Architect when doing something like this, not only for structural reasons, but window design as well. He will layout window detail based on the window sizes available from a certain manufacturer or you can take his drawings which indicate opening detail to a place who sells windows, and they have catalogs of window combinations and sizes to make it work with what you have.

Tsilanko, I would always recommend professional installation where needed. But what I am doing here is suggesting that WHEN you are planning to build or renovate, to consider how your plans will affect you in 20 or 30 years time. Split levels are very hep when you are young. A kitchen 3 steps down at 30 is rarely a problem, but might be a hazard at 60, or, as Marjie1059 suggested, if you break a leg. ... All my parents' homes were terrible for old people. They were forced to move to a bungalow in extreme old sge because the location and design of their home was more suitable for an active young couple with a large family than for an elderly couple with stroke disabilities. I would not want to move again, so my present home has features built in that make ageing in place simpler. Mostly small changes, like grab rails, and lever handles on doors and faucets. A major disability suddenly suffered requires major changes if permanent. I did look at this because it came up in the discussion, but if you look at the heading, Planning for Disability, it means just that. Plan ahead so you don't have to make expensive changes later on. But thank you for your advice, yes, major changes are not in the DIY domain.