I will take some pics of the damaged floor and the floor that is in better shape and post both. Thanks!

I was finally home early enough to get half way decent pics so hopefully I can load them properly. Thanks again for any insight! This is a close up in a spot that is not too worn....

These are the really worn/damaged areas that were under carpet in a bedroom and hallway. Any hope or should they just be replaced?

You have Red Oak. Plain sawn. As far as the stains, i learned a long time ago not to say if something can or cannot be sanded out. ive seen stains i was for sure were not going to come out, came out, and likewise ive seen stains i thought would and just would not clean up.

That black spot is suspicious. it may not come out, but i would definitely rip off the old finish and then see how the spots clean up if at all.

The nice thing about 2.25 red oak, is its very common to find that particular wood at home depot, at least in my area, so if you are trying to do this 100%DIY then you're in luck, if you choose to hire this job out, its not a difficult wood to find at all!

Good luck!

That floor is DEFINITELY fixable, except maybe for that black spot. Red oak is very forgiving and easy to find. YOu can

Look into "screening" - that's a light sanding followed by stain to even out the color and then a penetrating oil varnish topcoat. It leaves the floor looking like an old floor that's been well-maintained, and doesn't sand off much. It's a DIY project, because the equipment is easier to handle than drum sanders.

Here's a fix that was part replacement, part patching, and part staining to match a totally different wood.

http://ths.gardenweb.com/discussions/2466412/1890s-1940s-1990s-bath-update

If you're going to do something with the floor, do a full sanding. screening is not a viable option in this instance. you run the risk of have the finish not adhere properly, you have no idea kind of finish or gunk is built up on the floor, and screening will not do anything except make a mess.

start fresh, start over, and be glad you did.

I'll second the resanding advice. Chance of successful screening and recoating is close to zero. It's not worth the time and money to do something that's almost certain to fail.

Thank you all for the great info!! I'm leaning toward having it completely resanded because now I think I may re-do the other bedrooms also. Just hire someone to do the whole upstairs so everything matches. I don't think I can handle a drum sander - I'm too afraid I will damage the floor beyond repair! So I will leave the end part to the pros but I can get it ready - remove carpet, tack strips, staples, and clean it well! Thanks again - knowing the wood type is very helpful.

BTW, those dark stains are probably pet/ammonia stains and most likely will not sand out. Otherwise I think you'll be pleasantly surprised how nice it could turn out.

These stains came out. 1940's bungalow home Detroit. But I think the stains were less than seven years old according to the owner of the home.

the age of the stain does play a big role. Im on a job right now where these stains havent been touched for 20+ yrs. and they wont come out. the longer the stain sits and is able to absorb deep into the wood the harder it will be to remove.