I've decided on a layout/functionality for a responsive website and since I know HTML and a little CSS (learning more as I go along) I thought I'd code it from scratch, but am having trouble understanding how a grid system works....

So I've been looking at the many responsive grid templates around (Skeleton, Twitter Bootstrap, 960 grid etc.) except it's hard to understand what it's about in practical terms. Things like where to enter my content, how it actually works and so on.

So someone suggested I look into Wordpress and save myself a lot of grief and time. All I really know about WP is that it's basically a CMS based blogging system which relies on pre-designed templates, so I managed to install it locally on my Mac together with MAMP. That way I can play around without uploading stuff online. I do have some questions though:

1) Is it possible to edit the HTML and CSS in order to get a customized website to my liking/needs in the same way as coding a site by hand or do I have to settle with a theme made by someone else (most likely becoming a compromise)?

2) I'd like to have a search function for the site (it should also search through the site's existing and corresponding mailing list archive) but am struggling to find solutions for this. I understand that Wordpress has a site-search built in, which includes a MySQL database for indexing the site. Is this correct?