I agree with
@leonz on all counts. I'll add, with 300 acres you're not going to manage that much land with a compact tractor and a 3-point disc or plow. The very best thing you can do is find a farmer willing to rent new ground and go through all the expense and work to turn it into something productive. Said renter is probably going to want a longer term lease since they will have to invest a lot of time and money up front.
Soybeans and maize - you can probably find someone locally who does custom harvesting but you will want to make sure. Combines are not cheap, are more challenging to operate than a tractor, and are difficult to justify for only 300 acres.
What about chemical application equipment? And you'll need to get an applicator's license unless you're going to pay someone else to do the spraying, which is also expensive.
You need to also think about if you're going to row crop or broadcast. If you're going to row crop you'll need to look at bed preparation and cultivation. You can minimize cultivation with chemical application and round-up ready seeds, but there are pros and cons to that.
These are just of few of the things you need to consider before jumping off on a project of this magnitude with no experience.
As for vegetables, my hat is off to those folks who do vegetable farming commercially. It's a ton of work and requires a ton of expertise and equipment. I raise a decent size garden for our own use. Any more than that, and I'm out.
Good luck with your endeavor!