You are at the exact same point I am at now with mine! I asked the guy at the feed store because he raises chickens. Plus I'm moving mine to organic feed to make things even MORE difficult on myself...not to mention I just ordered MORE chicks to come next week! Oi!
Ok, back to your ?s...If you have them in the coop and there are windows, you can turn the light off sometime during the day and just let the natural light tell them when to go to roost. Thats what I am doing with mine and its working fine. If you are still brooding inside (spoiled at this age! lol) or there are no windows, it will be a bit harder because the chicks will freak out when the light goes out and they are in the dark. Their eyes work kinda like ours and need time to adjust to changes in the light.
As far as oat go, you'll want the highest protein you can get them in. At my feed store they come in 8% and 16%. I got the 16%, and also got the organic seeds (corn, millet, wheat, linseed) to make their new mix. You want to end up with them on a 18% protein ration by the time they are laying age. Right now mine are on their chick starter, that I've cut 80/20 with the oats and they LOVE it! They also range all day in the yard and eat yummy, icky bugs.
Within the next 2 weeks I will move them to a cut mix of more like 60/40 so that by the time they are 8 weeks, they can move to the organic layer ration I've made them (40/30/30), which to break it down is like 40% - layer grower pellets/30% - mix of corn, wheat, millet, linseed/30% - 16% protein oats.
Hope I helped a little!