Hi.
I'm not an experienced blogger but I've been doing a little bit of research, coz I'm intending to start my own too.
From what I've been told it's important to blog regularly, not necessarily every day, but at regular intervals - say every Tuesday, every other Wednesday, etc. - if you intend to blog everyday then you HAVE to do it everyday, because that's what your followers would expect.
It also good to plan your blog 5-10posts in advance, so that a you don't sit down on blog day with writers block, and also it covers you if you're busy as you have something on stand by that you just need to upload.
I can't say how long it would take, other than it depends how long your posts are. But as you get into the swing it should become easier, and therefore faster, to knock your posts out.
I don't know about traffic to your shop, but if there's traffic to your blog and links from your blog to your shop then presumably it will increase traffic levels. The more interesting your blog is, and the more original content on there, the more followers you'll get drifting through.
Here's a good article about blogging you can read, that is a how-not-to approach:
http://www.yourlifeyourway.net/2011/08/09/9-reasons-your-blogsite-isnt-bringing-you-clients/Marie.