Domain Name Same as Keyword, How Helpful?

Let's say you have the domain which is the keyword you're going after, how much effect does it have in google rankings? If it's a 3 word, rather uncompetitive keyword, should I eventually get the first place?

It will indeed help you in ranking. Lets put it this way, it couldnt hurt could it?

I already have the domain. I got it for the sole reason of getting this keyword so I was wondering if it's going to make much of a difference or if it's still most of the other factors that make the biggest difference. I've had the 1 year aged domain for about a week and I got it to page 1 number 10. Having troubles moving it up any further so I was just curious how much influence it had.

You already have the keyword in your URL so that's good.

Write an post/article for your homepage.
Put the keyword in your title and twice in your 1st paragraph of text.

Get backlinks to the page. Don't overdo this.
For a safe backlink strategy, check the board.

If I have a blog on the domain and I have a post stuck as the first post on the blog with a plugin does that work as well or would I be best off just making this a website out of html and css?

A blog is just perfect. Search engines (still) love them and there are all the build in promo tools like ping, RSS and trackbacks.

Don't know what plug you mean but you can make a post sticky so it always shows up at the top.

Here's the basic setup for my (whitehat) blogs:

I always have my main selling/preselling post setup as I described. This post will rank just as the home page.
Either this the last post I make or I make it sticky.

I get 2 flows of organic traffic.
Visitors directly to my "moneymaking" post and visitors to the homepage. There they see my "moneymaking" post right at the top.

I have a couple of sites where I target multiple keywords and these are harder to optimize than the blogs where I just concentrate on one longtail keyword and one product/service to sell with that.

seems to be good to have keywords in domain. I have haloreachonline.com which is right at the top when searching for 'halo reach online'