I understand what you're trying to do. I reiterate my original Follow-up, Echo, & More .... If you want a best-guess guess, call up a few contractors, have them price out a professional upgrade, knock off 30-50% for labor (which is their time and profit), ask a lot of 'what-if' questions, and see what you get.
W/O being able to see what's all there, and w/o being able to get a good grip on what you WANT to do (at least for me), then the aforementioned is what I suggest. For example, my parents got 3 estimates to remodel an existing kitchen (no wall-removal issues here). The estimates ranged from $14,000 to $22,000 depending on the contractor. One contractor admitted that his highest estimate was because 1) he has a reputation, 2) he really didn't want the job but if they were willing to pay, he was going to refer it to someone else and STILL make $$$. My father removed all the cabinets and ran the necessary electrical and plumbing lines. He hired a pro to hook everything up and got someone to do the floor. HE made the kitchen cabinets and put in a new window. He did all the finishing work (except the aforementioned.) The total cost when he was done: < $6,000 !!!
So, forget about getting anything reliable on the Forum because, well, there are too many unknowns and many, many more specifics are needed. ON THE OTHER HAND, if you want to know what it might cost to knock down an EXTERIOR load-bearing wall that's 25' in length w/electrical and plumbing lines in it, and put in an I-beam header, then, perhaps someone can give you a rough estimate. BUT, they'd need to know the current construction behind the visible wall. (Is it 2x4 stud, or what?) Does this all help you?