it sounds like you are where I was a year ago. Let wordpress handle the whole thing! never worry about title tags, meta tags, etc. The only thing that's generally editable is the content (as a designer, you'll know how to change the template files but clients won't). Set up a custom theme (overall look) with custom templates (the php bits like header, single post, etc). Paste the html into the proper php template file, then customize from there. Make sure to work off a duplicate, so if things get messed up the original theme can be turned back on/copied from.
One thing I did learn was to bookmark pages that are helpful, as you'll refer to them over and over again while figuring out how to modify the default theme to your own theme, and how to set up templates. Try a google search for learning wordpress tutorials -- the info here is good only if you know where it's starting from.
Also try MAMP, which runs an install of wordpress right on a mac. this way I can fool around setting up a theme without risking a live site.