If you are only just beginning to set up your mealworm farm, I recommend you watch a few video clips people have posted on Youtube. You will see how disgustingly simple mealworm raising can be.
It can be as simple as one 18 gallon tote, as you mentioned, filled with rolled oats or wheat bran. Toss in a carrot every so often, and walk away and forget about it for months, and come back and find a bin full of worms and darkling beetles. Sift out all the frass, harvest all the larva, add fresh bedding, toss in a carrot, and walk away for another few months.
Most of us do the three drawer method with the screening in the two top drawers so we have some semblance of order. The screening isn't to sift the waste. Its to permit the eggs to sift down so the beetles don't eat them. Rolled oats are good because they won't fall through the screening. If you use wheat bran, you are left with no bedding in a matter of days.
The frass (waste) is much finer than any of the bedding grains, so a steal-mesh kitchen strainer will work to sift it out of the still useable grain, whether you use rolled oats or wheat bran in your single tote.
Go watch a couple videos and come back and join the discussion. We'll all help you! This is a very satisfying enterprise, and you'll be hooked in no time! Don't worry, you'll be ready when your worms arrive!
I almost forgot to mention, you don't need any heater. But it helps speed up the process if your climate is on the cold side. I rigged up a simple heater using a 25 watt incandescent bulb in a cookie tin, placing it a few inches below my stack of plastic trays of worms. you can get a life cycle in weeks that would take months without heat. 80 F is the optimal temp.
