Hello there Broman..Welcome to the forums and its nice to see you making the move to the salty side of life..
Answers to your questions...
1) With marine fish keeping, what most of us tend to do is use the live rock and sand as the means of mechanical filtration rather than using things like cannister filters. To privide this, you will need to have about 1 - 1.5lbs of live rock per gallon for you tank.
2) Yes, there is such a thing as too much live rock..It serves many purposes in the tank, but one purpose it does is to provide the habitat in which the fish and inverts live. This means that each fish etc takes an area of the rock as its territory...its sleeps there, hangs out..But also, fish need to swim..So, if you pile loads and loads of live rock in the tank, the actual water volume gets diminished and the space in which the fish need to swim diminishes also..Another point of having too much live rock is that it creates dead spots in the tank where detrius builds ups which also causes problems..Plus, i think i think it look a mess with far too much live rock in there..
3) Besides equipment and live rock, one of the main things to think about is buying an RO Unit ( Reverse Osmosis Unit ). This device filters the tap wter to remove phosphates, metal particles, chlorine etc etc..All these in the water column promote algae growth which in time causes the tank to become unsightly..The other important thing to always keep at hand is loads of patience..this part is a must or else things go wrong, and can go wrong bery quickly indeed..If you want to know a list of basic equipment that you will need to buy, post what you have and i will fill in the gaps for you..
4) Lighting wise...This all depends on exactly what you want to keep..If its just fish only with live rock ( FOWLR ) then normal standard lighting is fine. If its going to be a Reef, then IMHO metal halide is a must..I would probably suggest something like upgrading the light to a 150 or maybe 200w metal halide and buy some T5 actinics as suppliment..Also, maybe a moonlight or night light kit so you can view the Reef when all normal lights are out..
5) Chemicals you are likely to need to buy is a good Saltwater test kit which tests for Ammonia, NitrITE, NitrATE, pH, Calcium and Alk at the very least..Other additives to keep at hand is calcium in either a dosable bottle or calcium reactor, Phosban, maybe iodine ( this is a debatable issue )..The additives you buy will depend on the tank you are running and how its setup..These here are just some basics for you..
I hope this answers your questions a little..By all means, ask anything you want and we shall do our best to answer..Remember, there are never any stupid or dumb questions, no-one will laugh at you here...well, i wont anyways...
Niko