Hi Maradri, Welcome
Is this your 1st name? If not would you mind sharing it?
Tim covered the basics. Do you know what kind of marble you have? (White carrara, statuary, etc.)
In the bathroom for example, you probably have acid etching around the toilet (round dull spots). This is caused by toilet bowl cleaners, or more than likely, the man of the house. If they're not too severe, can be repolished using powders.
Do you have dulling in the traffic pattern areas, or throughout? (Doorways, halls, etc.)
How about scratching?
How's the lippage?
What kind of grout was used? (sanded or unsanded)
You mentioned staining. Where are the stains located? (Next to the tub, under the edge of the toilet, etc.)
This is truely not a job for a homeowner. Buyer beware, as many alleged proffesionals, should not be allowed to tackle this process either.