There is a test you can perform to determine whether your floors were finished with polyurthene, but I can't remember exactly what it is. Search through some sites on wood floors and refinishing and you'll find it.
If they are poly, you should never put an oil or wax based product on them. You will make them tooo slippery, and afterwards, they will need to be sanded to bare wood in order to refinish.
If they are poly and no oil, wax, furnature polish, or similar stuff came in contact with them, then you can screen sand lightly and apply another coat of poly.
Now, you may want to determine whether the wood is protected well enough. You can do the water test, put some water on suspect area and watch for 1 minute. Does it bead and sit their, slowly get absorbed, or quickly absorbed?
If your floors are properly protected. Maybe you don't like the finish? My floors have satin finish poly. They look like bare wood but their protected. This is ideal to me because the lack of shine hides the dirt. If you go with high-gloss poly, every speck of dirt will show up and the floors will always look dirty. So consider what you want carefullly.
Bruce and other manufacturers make specific products to clean hardwood floors finished with poly. These cleaners work great. Bruce also makes a product to restore the beauty of warn areas. I have not tried this one yet. I wonder about it because I have satin finish and they only have one type of restorer product?
As a final note, if you have satin finish and want more shine, a light sand and top coat of higher gloss poly will do it for you. Just remember the dirt factor.
Good luck. Any more specific questions just post em up.