If the finish on the floor is intact - it is advisable to have flooring specialist to come in - "rough up" the surface & apply a coat of poly (if poly is what was used on the orig finish - this can be done if no oil based products have been used on the floor) I would contact a Hw floor person to advise you - We put HW in kit & were rec to do a coat of poly every 1-2 yrs - this way, a sanding/refinishing is not necessary -

Thanks, Lynn2006, for finding that link -- I looked all over and couldn't. I found some places I could buy it in the NYC area; but do you all think it will be the correct product for my purposes, or is there anything else you'd recommend?

You need to do a little more archeological digging still. You need to know the whole construction of the floor before you can decide how best to install something new. I'd take up that plywood piece in the kitchen and see what's under it. It's higher than the surrounding floor, so needs to go. You should also be able to see from there what subfloor is under the original kitchen hardwood. It's too bad the space under your entryway is finished, but I'd still do some exploring from below to see what's under there, and to figure out the fix to stop it from squeaking. Is it drywall below or a drop ceiling? I know it probably seems like a pain to tear out drywall, but if you cut out a clean patch, like 2' x the width of the joists, it'll be relatively simple to repair. Just make sure to cut it down the center of the joists so that there's room to screw the patch piece to it later. Cut the hole under the area that squeaks the most, if you can. Have someone walk on and watch the floor from below to see what's moving. It might be as simple as pounding in a couple shims from below, or face-nailing a loose board from above. You want to find out what's underneath the hardwood. It might be laid directly on the floor joists, or there might be 10" wide boards that the hardwood is nailed to. Another thought is to take out a board in the hallway, since that's not original and you want to replace it. See what the subfloor is there. I am a bit puzzled at why, when you've stripped the kitchen down to the original hardwood, it's still higher than the hallway floor. Is your current surface perhaps not the original kitchen hardwood? Peeling back the plywood area will help determine that. BTW, I haven't heard of that stop squeaking product you linked to, so can't offer any personal opinion. And don't pour self-leveling compound over top of hardwood. It needs to go over plywood.

I must admit I don't bother washing our wood floors, preferring to spot clean with Pledge MultiSurface wipes. We have Swedish finished oak floors and when I have an area that needs a deep clean I use mineral spirits, applied with clean, old white tees. It really cleans well and leaves a nice shine, without making the floor too slick. You will need to do a test on your particular flooring to make certain the spirits won't lift the finish. (Pick an out of the way corner and use a clean white rag - rub gently with a circular motion. If you see any of the floor's coloring on the rag then don't use the mineral spirits. Or if you have a spare piece of flooring somewhere you can use that as a test board.) Make certain the room you're working in is well ventilated - I always work with a window or door open.