I usually place the root tip down and just barely cover the seed up with loose soil.
as per the hid light both high pressure sodium and metal halide are hid lights and if your only going to get one type would suggest you get a high pressure sodium while metal halide has a little better spectrum for veg and hps better for flowering you can get by fine with just one type and seeing how flowering is most important you should probably choose a hps.
and the link you posted doesnt have any hps ballast that I saw, they do have mh ballast.
the link in your first post at 1000bulbs does have hps ballast, reflectors and socket cord assembly all made by sunlight supply under horticulture lighting section if you wanted to buy a complete system, your other option would be to buy a multi tap ballast kit and ballast box and socket and bulb and you wire it up and install the socket in your own reflector or a homemade reflector.