Well why I stress not to try it, I will stand by your decision and help you the best I can.
Lets go over some things from the page that you had me look at.
I agree you need as much live rock as possable, which isn't going to be too much in a small tank.
I am unfamiliar with no sustrate like he suggests, I always used a crushed coral sub. But this is up to you.
I agree to use only mushrooms , and I wouldn't even add these for a while!!
hermit crabs are a nice thing to add..but I also suggest a few turbo snails for algae.
I myself, used tap water. Check your Tap for nitrates, which not everyone has them added. Phosphates can be takin out with a phos-zorb pouch, which can be placed in your skilter if you get one, which I would!!!!
A skilter used bubbles to adhere disolved organic compounds. It raises them up through a chamber and dumps the junk into a holding compartment.A benifet that I wouldn't pass up. It does however, get rid of some vital nutrients that you have to add back into the system.
I dont know how long his system has been up, but 3 weeks is too long for me to do a water change. Weekly to bi-weekly, and you will find the algae loves the front of the glass to grow on.
You will need a full spectrum bulb, and a actnic bulb 50/50.
He doesn't use addatives, but it wont hurt if you get a all in one supplement, to help replenish the ones used.
You must use a hydrometer. You need to measure the salt in the existing tank, which will increase in salinity due to evaporation. Then lower the salt added into the water your adding for a water change.
If you dont do this, you will have too much salinity in the main tank .
On a side note, his tank could still crash where everything suddenly dies off.4 monthes is not really a mature tank in my opinion. Lets see after a year how he is doing.
For marine fish only, you would have greater success for a beginner.A skilter is all you would need for a 10 gallon.