Not to be obtuse, but it depends on the purpose of the valuation. If you want a general idea, ask your insurance agent, especially if your policy allows for replacement value (it's also free). If the purpose is for estate reasons or for refinancing, an appraiser is the best choice. An appraiser can also use replacement value formulas and other factors they use in their practice,as the appraiser below elaborated. That will probably set you back $400, though. If your purpose is for resale, hmm, that's a toughie, because the market will determine the value.
Forest Heights is a desirable area, but sales of high end homes on your part of the West Side have really slowed down, lately. But truly unique houses always seem to draw buyers. Think of it this way: If a buyer saw ten homes in the perfect neighborhood for $800k, which house would he/she buy and why would he/she choose that one? It won't be because it was the cheapest house, it will be because it was the most special to that buyer.