I agree with getting your AG agent out, he will make recommendations for free, "boots on the ground": so to speak. Ditto on the soil sample as well.
1/2 acre garden is pretty darn big, possible, but you may want to try smaller and in the mean time, maybe plant some fruit trees?
I'm with the tiller idea if you can swing one, just remember as good a job as one does, you will only use it 4-5 times a year (but hard to beat) During grow season you will likely need a smaller tiller for between he rows.
I bet you could get a farmer close by to plow it for you, good way to meet a great source of info too. Personally, I would pass on using weed/grass killer, not necessary IMO and could be there awhile possibly. They didn't use it in the old days and did quite well.