Since no one else has answered, I'll chime in here. You could post this in the Oklahoma or Vegetable section or see what is offered at local garden center in your area. Seems like too much for one bed. For corn, use seeds and you'll need a block of it so they pollinate correctly. Say 9 plants, about a foot apart. For tomatoes, since you're newbie, I would suggest getting already grown hybrid plant for first time. Squash and cucumber sprawl and take up a lot of room. Green beans are easy from seed and are smaller plants so you could probably squeeze in a bunch. I suggest you shorten your list and grow what you like the most. Good luck!

You could check out square-foot gardening.

As far as soil for raised beds, I use: 1/3 vermiculite, 1/3 peat moss, and 1/3 compost (usually manure or my own). Or you can just go pre-made. I've have success both ways. Usually the vermiculite mixture lasts season after season--whereas pre-made soil I have to mix in some new compost every season.

Tomatoes can be little babies, there's nothing wrong with hybrid plants--it's not like they're GMOs. I'd go hybrid for your first go-round so you're not pulling your hair out. Also, grow them from started plants if you can (if you're doing tomatoes).

I also agree with Jerseygirl, shorten the list and grow what you want the most. It'll save you a lot of time and stress!

Carrots, cucumbers, and beans are easy to grow with little problems (in my experience.)

Go to your local Home Depot or Lowes. What you see there in their plant and seed section will give you an idea of the kinds of veggies you can grow in your area.

Corn and beans are easy to grow from seed directly planted, so you won't see too many starting plants of those at the store (though I did see corn starts for the first time recently)

The reason you get conflicting reports about what kind to plant are because of people's tastes and experience. Hybrids may be good for something such as being disease-resistant, but growing a new plant from seed may be different from the parent. Heirlooms are good for saving seeds and planting again next year to get the same type of plant and veggie/fruit.

But if you don't save seeds, then that won't make a big difference to you.

Another example would be that a tomato is a tomato, or is it? A friend doesn't like Roma tomatoes but she eats beefsteak tomatoes, so for her, she would choose one type of tomato over another.