Since your thread is in classifieds, I assume you're looking to buy stuff here? Craigslist has some good stuff for sale too.
300 acres of wheat, oats and corn? I'd say beyond a nice size tractor (say minimum of 65 hp) you'll need: a big sprayer, plow, disk, cultipacker. You'll need a seeder/fertilizer for some things, depending on scale OR drill, etc. For corn, with 300 acres (if you did ALL in corn) I'd say you'll want an 8 row planter minimum, bigger if you can. I mean, I can do 300 acres with my 4 row BUT it would just take SO LONG! Now, for fertilizer, lime, knifing in N & spraying - I'd actually contact the co-op or some farmer in your area that can help with the custom application of that.
LAST- you'll probably need to work with farmer on getting custom combined/harvesting. If you wanna combine & harvest your own stuff and haul away (or store) - you're into a whole extra area of expensive stuff you WON'T want to mess with for 300 acres. Custom will be key. you gotta get with some local farmers in your neighborhood that are trustworthy and discuss all this stuff.
Other options would of course be totally custom farming, crop share, cash rent, etc.