Hi Kewkew,
Some great advice from Thomas, so I'll try not to repeat anything he's mentioned.
I see two options at this point. Take out the larger rocks and any roots and grass clumps you find, add 4" of compost, till it into the soil and plant. Cover the soil with 6 layers of dampened newspaper and about an inch of shredded bark mulch to hold it down. Be sure to dampen the newspaper as you work or the first breeze will have you chasing it all over the yard. Been there...
You will probably have to weed out grass that sprouts because it wasn't removed before you tilled the first time, but the newspaper layers will help to smother some if it, along with weed seeds that might sprout.
Another option would be to to do the above and then cover the entire planting bed with plastic to 'cook' the weeds for 3 to 4 weeks. You won't be able to plant seeds until late July or August, and then it would be your cool season veggies such as carrots, beets, spinach, lettuce, green beans, etc.
Here's a compost calculator so you can determine how much you will need.
http://www.cedar-grove.com/compost_calculator.asp
Some veggies are cool season veggies and some are warm season veggies. Considering where you live, at this late date you would do better with transplants instead of seeds for your warm season veggies. You should find these sites very helpful.
http://urbanext.illinois.edu/veggies/directory.html
http://www.gardening.cornell.edu/hom...scene0391.html
Here's a handy site on when to start what plants from seed. You'll need to know your first and last expected frost dates. That's the second link.
http://www.chestnut-sw.com/growform.htm
http://www.victoryseeds.com/frost/
Here's more help on when to plant what. This site is from Kansas which is in hardiness zone 5. I don't know your zone, but you could be in zones 5 or 6, so the dates are close.
http://www.savvygardener.com/Feature..._calendar.html
You can check your hardiness zone here.
http://www.gardenweb.com/zones/zip.cgi
http://www.hort.purdue.edu/newcrop/c...ps/IDhardy.jpg
When to harvest veggies.
http://www.savvygardener.com/Feature...egetables.html
http://pubs.caes.uga.edu/caespubs/pubs/PDF/C935.pdf
If you have any vining veggies, you might want to make this trellis for anything you grow that is a vine.
http://www.doityourself.com/stry/vegetabletrellis
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.