You could hire a pro to do the rough work for you. Hopefully, you'll find one that knows how to deal with load-bearing walls and any other 'issues', such as electrical or plumbing, that may 'pop up'. After that, you could do the finish work. To me, in lieu of your hesitation, you could spend 'good money' on having a pro come in.
It's just a thought. I've done it this way before I got 'better' at it. Well, in short, when there's been a load-bearing wall to deal with, I've opted for a pro to rough it out because I don't know how I'd explain to my Insurance Adjuster why the 2nd floor is now on the 1st floor.