hi andy,
just a couple of questions first,
are you re-sealing with polish or with varnish?
if you are using polish i would do it the same way as previously mentioned,
if you are sealing with varnish or oil, i would ask which seal they used before was it water based or oil based, how long ago was it done last, what have they been cleaning it with.
if they are not sure with the questions here i would strongly recomend that they would resand the floor,
and if thats the case we could sub for you, if you would like a price email me at
castlecleanings@aol.comi can give you a really competative price and you can add what you like on top,
thanx jonny