I wish to place a door in a non-load-bearing partition wall. It's in a low ceiling height basement, with only 6'8" of headroom. I want the door as tall as possible, and need to know what to do. I was just going to use the top plate of the wall as the door header, but thought I should ask here for advise.

I've read a couple of threads on replacing damaged subflooring, which provided some excellent advice. However, I want to get just a little more specific. The damage to my subflooring is right up next to the baseboards (and probably under it) due to cat urine, but just in certain areas (thank goodness, it's not everywhere). We are going to have new carpet installed next week and I want the odor gone. Yesterday, we pulled up the carpet, and the floor and tack-strips are black with stain. I think we should replace the subflooring, which will totally eliminate the odor, but my husband says that we can't because it runs under the wall. By the way, this is first-floor plywood subflooring over a basement. I have purchased "Urinine-Off", which is suppose to take out the odor, and we are going to seal it afterwards with either polyurethane or Kilz (don't know which one is best). There appears to be so much damage that I'm not sure the solution will work. Can the subflooring be replaced? If so, how with the minimal amount of work, and is a week enough time to get this all done? I need an expert's opinion in order to convince my hubby to do this. Thanks.