I'll put in my two cents......

If you got a large weeded area and you're
concerned about using chemicals to treat the
weeds then you should look into a propane
weed flamer. They're safe, very effective,
and some models are quite inexpensive. They're
also great de-icers btw but thats probably not
much of an issue for you in NC. A web search
should turn up lots of options.

Basically you just want to scorch the leaf of
the weed so just a brief pass will suffice. If
you've got big ol dandelions with deep tap roots
you may have to hit 'em a couple of times but they
will eventually give up the ghost. Im not going to
lie to you. On a lot your size you're looking at
a good dose of work but you might be able to find
an organic lawn care company in your area that'll
use the flamer. They're not uncommon.

Once you get the weeds under control start seeding
like there is no tomorrow. Lots of other guys on
this board will know more about specific varieties
than I do but it sounds to me like you need to just
get a beach head going so I don't know if this is
the year you sink $$ into higher quality seed or
not. Maybe you wait till next year once you've
got things under control. You'll get lots of
advice here on that one.

Whatever you choose to spend on seed take this advice:
Pull a weed, drop some seed.

As soon as you get your weeds under control you'll want to
address your soil issues. Weeds are like messages from the
soil telling you whats lacking in your soil. Clover thrives in areas of low fertility, Creeping Charlie in
areas with poor drainage and so on. ID the prevelant weeds
and get a handle on what kind of enviroment they thrive in.
Then you'll have a grip on whats happening, or not, underground. You can also send some samples away and get
a soil test. Do what the results tell you.

If you want to continue with a non-chemical approach
once you've got the upper hand you can fertilize with
Alfalfa Meal or Soybean Meal which is easily found at
feed stores or you can go with a retail product like
Restore or Cock-A-Doodle-Do. In my area Scotts has an
"Organic Choice" lawn fertilizer which is actually pretty
good.

What I've described is a lot of work but its much
cheaper than what most lawn care companies will likely
charge you and there are absolutely no risks to pets
or kids or anyone else in this approach. For what its
worth I faced a situation for much like yours, though
on a smaller lot, and turned it around in a couple of
seasons with only organics.

Good Luck.

Where in NC are you? Your general choices are going to be a bermuda lawn or Tall Fescue. Bermuda will look great in the summer but does dormant in winter. Fescue will look great in spring and fall and decent in winter. If you water it in summer, it can stay nice, but if not, it will brown out if we aren't getting consistent rain. If you want Bermuda, now would be the time to to get rid of weeds and seed. If you want fescue, you can start controlling weeds this summer and prepare to seed in september.