If you ignore any of my other advise, please just listen to this,
Always always register your own domain name with 123 reg or the like, this way you have control over it, every second of every day...
I would register the domain name today, you have given people an idea of a domain name, ( if I were browsing and came across this, it would be too late for you ) set it up as a holding page with what you intend to sell on it as an intro. It doesn't have to be pretty, you will see why in a second. ( If you need help with this pm me )
I would also submit it to a website, any website will do as long as the page is indexed by google. Never submit your own site to search engines, at least until it has already been found by SE.
As soon as possible, when you decide what to sell, make a mini site on your computer, write descriptions, find pictures, think about how you want your site to look.
The more effort you put in now, the better you site will be, if you don't go ahead with selling on the site, you could sell the domain name and site
Good luck.