You can try to learn all of these skills yourself but it can be very time consuming and you will probably end up with a less than ideal final result. You can use something like Twitters Bootstrap. Bootstrap is generally easy to learn and quick to get up and running. The main drawback is your site will look very similar to many other sites. Another option would be to hire a freelance designer. If you want a unique website this is one of the best options but comes with a few drawbacks. You need to find the designer, communicate your vision, then hope it turns out well while you wait for the work to be done. Also be prepared to pay a hefty price tag. Depending on your company size, branding and how unique you want to be it could very well be worth the money.
A final option mixes a little bit of all the previous options together. You can learn bootstrap and purchase a theme / skin to make it look much more professional. Sites like wrapbootstrap or themeforest can provide very clean designs at much more affordable pricing. You will still need to do quite a bit of the work yourself but you also learn along the way. Your site will be more unique than Bootstrap but others can still buy it so it's possible to have a site look like someone else's.