i think there is only one official
DVC tour - at SSR, it's a tour of the BLT and AKV models.
there is also sometimes a tour at BLT - i don't believe you would get extra benefits for doubling up on tours. really, just go if you are interested and don't waste your time if you are not.
there is also a model of BWV set up on the boardwalk. not an official tour, but it's worth wandering through if you are interested.
you should be able to contact DVC to set up a tour by going to the DVC website - otherwise, there are a million kiosks at wdw that are hard to miss.
if you want to see the inside of another DVC resort villa, like SSR, you would have to go to the lobby and ask the personnel there if they have time and a free room to show you. if they are busy, they may not be able to assist you...DVC has no official policy for showing rooms at sold-out resorts.