buying a used tank for a first effort

I have read 4 or 5 books on marine aquariums as well as this newsgroup and
most of the links people provide, yes, Marc, I have read your pages also,
they are probably the most informative.

For my first try at a marine tank, I am buying a 29 gallon "established"
~minireef from someone. In the tank is about 50lbs of live rock as well as
about 1" of sand sitting on the bottom glass. There are a couple of corals
and a sebae anemone. The previous owner has a filter and a powerhead that
sweeps back and forth.

I wanted to do away with the filter and add 2" more sand to the bottom to
create a 3" DSB (can that just consist of 3" of sand sitting on the bottom
glass?)

Concerned that a UV sterilizer and some way to process the water through
charcoal does not seem to be provided, I guess getting the filter from the
guy would be a good step, but I understand that the filter would breed
nitrates.

Is the filter going to really offer me anything or should I just invest in a
pump and a canister with charcoal material and nothing more ? Can I do this
without causing an increase in nitrates ?

The powerhead sweeps back and forth providing what I would assume is an
inconsistent water flow around the tank. Won't the fish better appreciate
the current to stay the same way ?

If the powerhead fails my tank won't get any oxygen since motion on the top
of the water would be non-existent. Does it make sense to have 2 powerheads
in the event that the first one fails ?

I have read a little about R/O systems. Why can't I use dechlorinated tap
water with IO added then age it a while before use instead of starting out
with R/O water.

What is the best way to move this tank, distance about 20 minutes of normal
driving?

When I add the extra 2 inches of sand will it be seeded without the tank
cycling ?

My intent for this tank will be to try to get some clownfish to breed, what
can I have in the tank that won't **** off the clownfish ? Can I have a tang
or two ? What kind of scavengers can I have that won't eat the eggs but
will keep the DSB clean ?

Thanks in advance