We are replacing the flooring in our house, and I have a few questions.

Throughout the house, there are areas that squeak when you walk on them. I've got the carpet up, and we plan to screw the subfloor down to the joists. Is there any particular size or type of screw that we should use, and how far apart should we put them. Should we only tackle the areas that are squeaking, or would it be worth the effort to go ahead and do the whole floor while we have it exposed? (Our house is 21 years old and we only have one layer of plywood as a subfloor)

Also, in the kitchen, we currently have sheet vinyl (which is going to be replaced as well). There is a bad squeaky spot there too. Can we screw down through the existing vinyl, or would it be better to try to remove it. We will be having new sheet vinyl placed in the kitchen, so I'm sure they will use a leveler product on the old flooring--- will that cover the screws? Also, currently, the adjoining family room is carpet, but we are going to have sheet vinyl put in there too, so will the leveler take care of the difference in height between the old vinyl and the bare subfloor?

We're thinking of putting vinyl in the kitchen, family room, hallway, foyer, utility room, and hallway. I haven't spoken to anyone about expenses yet, but we do have a guy that I plan to have do the work--- because he did a REALLY good job for my Mom. How much does it usually cost to have sheet vinyl installed?

We would like to have hardwood put in the bedrooms, living room, and dining room--- probably engineered wood. I'm a little concerned about how it will hold up since we have two indoor dogs. I had been leaning toward a higher end laminate, but some of the laminate products seem to be as costly as the engineered hardwood. Does anyone have any recommendations of brands, or any advice to offer on making a choice? We are thinking of maybe trying to do it ourselves, but have never done anything like this before, so we're a little nervous about it.