I'm using old masters espresso stain over red oak new hardwood floors. Do I need to use a sealer or will 3 coats of Duraseal matte finish be sufficient?

1. 24 hours as stated on can of stain
2 as stated on can of water based poly
3 let dry 24 hours before using it or as stated on can of poly

1. Sweep, dust or dry mop daily.
2. Vacuum weekly.
3. Clean heavy-traffic areas with a damp mop twice a month.
4. Clean with recommended hardwood floor cleaner once a month.
5. Apply a fresh coat of finish every three to five years

Ad color stain to suit. Oh and this section is for car and truck questions. Just saying...

Spray the oak floor with a 50% solution of white vinegar solution mixed with water and let stand for an hour, then clean with hot soapy water. Alternatively clean the floor with a steam mop, as either method will kill the mould on your floor.

Usually a good cleaning will do. The factory finish is very tough and hard to ruin. ( polyurethane with aluminum oxide).
Usually these gloss manufacturers also make strippers for their finishes. Try using that in a hidden spot and go from there.
Read Instructions & Follow them thoroughly.

You need a reducer strip. Find a local hardwood flooring supplier and tell them the height difference between the two floors and the length of the opening. Once you have the right reducer find a wood stain that matches your floor. Next stain the reducer and finish with either a high gloss or matt finish polyurethane coating available in a spray can. Once the piece is finished your ready to install it. If the subfloor is wood then you can nail it down and putty the holes. If your subfloor is concrete then you will need to glue it to the floor with some liquid nails. Apply the glue to the bottom of the reducer put into place and weigh it down for 24 hrs.

http://www.ehow.com/how_5098704_clean-pet-stains-oak-flooring.html try this bud