First grow attempt, need help

Hey guys, i'm sure all of this has been covered in other threads but i can't seem to find the exact information i am looking for so any help would be greatly appreciated.

I am looking to start growing a few plants... as many as possible really.
The grow tent i have sourced for my location to grow is 8ft wide, 4ft deep and 6.5 high.

To start with i will be growing from seeds, but once a few are up and running i plan to start cloning.

What i mainly need to know is how many plants can be planted in this space. How many plants per sq ft? The system i plan to use is an ebb/flow system.
What kind of nutrients do i need to be adding to the water and do i need to keep regular check on pH levels?

Also what lights i need and what wattage they need to be. I have been looking at a few with both Metal Halide (MH) lamp and High Pressure Sodium (HPS), but with only one socket. Will i need 400W, 600W,1000W or a combination? At what stage do i change the globes?
Is 18hrs on and 6 hours off correct for the lights or is that only at the growing stage?

I understand with these types of globes ventilation is required, will an exhaust fan be enough or do i need some sort of fan circulating air as well ?

Because it's in a tent will i really need to bother about a CO2 tank on a timer? I have been told to get one and run it for 1hr per day (with the fan turned off).

As you can tell, i am new to all of this so any help will be greatly appreciated.
I just want to get up and running as soon as possible.

Thanks Gibbo!

I cant comment on the ebb/flow system as ive had no experience with it, plants per sq ft ultimately comes down to strain (indica/sativa), how youre going to control the growth of your plants, maintanence and floor/wall space for all your control systems, air circulating fans, extractor and fresh air fans, resevoir, size of lamp, distance from plants etc etc
I use T5 flourescent for seedlings and veg and HPS 600W for flower. If your cloning youll need 2/3 rooms for different environments, light settings and light distances which means more control systems, more light systems and timers etc
If the ebb/flow system is hydroponic then PH levels are critical as are PPM so yes regular checks needed. Plus digital meters for PH, PPM and PH adjusters. Speak to your local hydro shop for nutrients. Your bulb rating, number of lamp units, ballast units, contactors and timers will come down to calculating how much space you lose in the grow room by everything you need to control the environment then see whats left for plants. Choose your wattage from there but ultimately the more juice the bigger the yield. Fresh air is vital as it contains CO2 which is obviously vital to the plant, so provided you have a fresh air supply and an extractor fan big enough to get the hot air out your ok without CO2 but the more CO2 during flower the better and yes turn the fans off at the same time so the plant can use the CO2 d0ct0r