and a career as a web designer will certainly be that much easier if you have at least some sense of design. People buy with their eyes to a large extent, and a site that works well and looks good will always attract more traffic than one which works well but looks pedestrian.
Apart from that, you'll need some technical knowledge, and that can only be gained by working hard. There are several lines of attack; reading certainly has its place, but above all practice is what helps. Get hold of some decent design software - DreamWeaver, or Expression Web, for instance, and a good image-manipulation application like Photoshop or (less expensively) Ulead PhotoImpact. What you don't need, if you're planning to work for yourself, is any formal qualification.
Then practice - open a webhosting account and buy a domain name. Design a site and publish it to your account. Tweak it and design some sub-dommain sites, then tweak those, too. Practice and practice until you know the software pretty well. Look at lots of other sites and learn about design - what looks good and works well. Learn about copyright, and some basics about online selling, and learn about how shopping carts work.
Then, when you think you're ready to start charging people for your work, find your first client. In most cases this is the hardest part of all - people want to see previous sites you've designed, and you don't have any. A good ploy is to contact some local charities and/or businesses and offer to design a site for nothing. You're bound to get some work that way, and suddenly you have some previous work to show real paying clients.
It isn't easy, and it won't happen overnight, but if you have design talent, and you're prepared to slog at it you'll succeed. If you have no flair for design it might be better to consider some other ways to earn money, because competition is very stiff - there are literally hundreds of thousands of other people out there, doing what you're trying to do.