new marine set up

hello
i was wondering if anyone could give me advice.
we are thinking of converting our tropical freshwater tank to a reef
tank, with coral, inverts and some fish.
we have a 350l tank (juwel trigon 350)it has a internal filter which
pumps 1000l/hour (aparently)which includes a heater, and 4 flourescent
bulbs built into the hood (2x 36" and 2x 15")
Our thoughts were to have about 30kg of live rock, a skimmer (probably
the Deltec mcE 600 hang on)4-6" of sand (would live sand be necesary?
and do we need this depth of sand?) 2 or 3 powerheads (each with an
output of 1000l/h)and replace the tubes with 3 marine white tubes and
1 blue maine tube. We would also replace the filter media with
efusubstrat.
does this sound ok or do we need to consider anything else.
we would, of course, be buying a reverse osmosis unit, salt,
hydrometer, testing kits etc.
any infomation would be greatly appreciated.
thanks
linzi