Hi there Micayla. It is a big decision to dread when doing a method that is not instant. Twist & rip dreads are less damaging than back combed. The reason being is that the hair is "teased" when back combed, that does cause some damage, cracks to the strands of hair. T&R, if done gently, does not cause any damage that I know of, at least mine did not. So the order of what is best is...Neglect/free form....next is T&R...then back combed.
As for your oily scalp. When dreads are mature, which takes a year - two years, depending on hair length when starting, that is when you should only wash once a week because mature dreads can take 24 hours or more to completely dry, depending on the thickness. Believe it or not, by that time the scalp and hair adjusts and does produce less oil. I too had oily hair, now I can go a week at a time if I want to. For the first 6 months or so, you can wash as often as you want or as often as you need to. The hair is not locked up yet, so it dries in just a few hours.
If you do back comb, please don't let anyone add anything, especially wax, to your hair. Wax prevents true dreading and has too many problems with it, like trapping water and causing mold.
As for sectioning. That you can start right away if you do decide you will dread. By just not combing or finger combing or conditioning the hair, it will form into sections all on its own. That is the best way, then your hair goes where it wants to, not where it is forced to. After those sections form within two weeks, you can always divide them smaller if you find some are too large. The mature dread will become the size of the section where it meets the scalp.
I have some tips that will help you, I did T&R, but you can use the tips for back combing also: http://www.dreadlockssite.com/forum/topics/just-starting-out-what-to-expect
Dreads are clean, not dirty as some think, so it is normal to still wash 2-3 times a week. Oh yes, purchase a dread friendly shampoo.
Please ask any questions you need answered, we are all here to help....hope I answered everything...peace