parquet floors

so what is the best way to refinish parquet floors? the ones in my house are about 90 years old and have probably never been redone, but look like they're in pretty good shape underneath, bad top finish and some water damage though. i'd much rather refinish and keep the originals than get a whole new floor. also, can anyone tell me how much i should be paying if i do end up paying someone to do it? i live in the DC area.
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