no need to make it, it's already made, just like any other software.
upload it to your webspace, if you have other content there that you don't want to lose, then place it in a subfolder.
have you checked the demo? it has a pretty easy and clean interface.
got no idea what you're talking about here.
Good luck, there is no such thing as the best one - and sometimes only after using something for a prolonged time, do you find faults with it that are not good for your business. Magento at least you can try out for free, but I guess you don't want to invest that time, fair enough.
well, you could always buy the Magento handbook for $25 or hire somebody to set it up for you as well. Free & open source software doesn't mean that there is no paid support available, difference is that you don't need to pay that monthly fees for products that often times don't come close to what open source alternatives can provide - particularly when it comes to software for the web.
But at the end of the day, it's your call.