Wow, if there was any way to go with corn, that would be _the_ crop to follow an old alfalfa crop with - you are getting 150 lbs of free N for the corn, and chemicals to kill off the alfalfa will be much easier. Roundup can do it, but need a lot.
Really kinda throwing money away by going to beans, unless corn just don't work in your area.
Don't mean to try to tell you what to do, but if you are new to crops, you really need to look at your crop rotation choice?
The singulation meters will cut down on your seed costs, better stand. On 30 acres, it probably isn't so critical, but... they are better certainly.
7000 is a bit of a light planter to set up for rugged notill, but for your acres it should work out well, will spend a few bucks per row but stuff is out there. If the ground is hard some have put sand in the insect boxes (chain off of course) to weight the rows down so the depth goes down good enough.
Shoup is a good source for parts for a 7000, cheaper than JD, more friendly than some of the super-big dealers any more, and parts are just as good. They are online, but the printed catalog is easier for me.