db3512 - I have just recently (last 12 months) finished removing my fireplace. It was a double sided version of yours. 6 feet wide and 5 feet thick. It was not an easy task! First, this is a best guess. The brick from about the top of the flue on up the ceiling will likely be backed by framing and a header; no drywall. Below that it will likely be part of the firebox structure. You could conceivably remove it with a lot of work and mess. A 5-7lb sledge works best to just splinter the brick. Get the one with a wedge shaped end. It breaks the brick better. The brick breaks easier than the mortar so don't waste your time trying to chip at the motar. Once the upper brick is out, the mortar generally comes out pretty easily. I would also wait until spring as your heat will go right out the new hole you have created. If you can, get into your attic and look down along the chimney to validate. I could see the entire back side of the brick walls down to the firebox. About widening your firebox, in short sure if you have enough money you can do anything. Not to be flip but if you want to enlarge your firebox, you are looking at tearing out your fireplace and rebuilding it. Again that assumes it is a real fireplace and not a brick façade of some sort. Good Luck!!

Unfortunately, because brick is so porous, it's very difficult to remove paint from it effectively as the paint absorbs into the brick. The best way is to hire someone to sand blast it (which will also clean the entire brick front), however, this method is pretty messy when done indoors. If it's just small drops you can try scraping them off with a wire brush. But be careful not to brush too hard as brick is relatively soft and the brush can leave marks and/or discolorations (try it on a small area first). Paint remover can also work although it may not be effective in getting the paint out of the pits and recesses in the brick. As far as cleaining it goes, it depends what you are trying to clean off. If it has whitish deposits you can acid wash with muriatic acid (pool acid) but be sure to follow the directions carefully and wear gloves and eye gear. If it's soot, some household cleaners may work. If you decide to have it sand blasted, that will clean everything off. Hope this is helful.

pressure washer, if that doesnt work, get a professional P washer out that has a heated wash system..... should take it right off... worst case take out the pavers in that little area, flip them, and re set

Eh, I'd think something like this would vary greatly depending on your particular fireplace, the labor market in your area, the tile and style of surround or whatever you want, etc. Hopefully someone could give you an anecdote or ballpark figure, but I still think a quote from a specialized local contractor would be best.