Hi, a quick question. I've overstayed my Visa in S.A due to some issues, I need to go back home asap. My worry is; are they going to detain me for overstaying or they will ban me and let me go?

If you were arrested on a count of fraud or drug smuggling you will be deported after been detained by the immigration section of the country.
If you have overstayed like a month or so, you will have to pay a fine for over-stay and subsequently provide good proof for that otherwise you will be ban for 2-3 years from entering the country again.
Hope your passport is available to avoid harassment by the section of Nigeria Immigration and Airport authorities.

WallFlower90:
Hi, a quick question. I've overstayed my Visa in S.A due to some issues, I need to go back home asap. My worry is; are they going to detain me for overstaying or they will ban me and let me go?

U won't be detained but will be asked to present ur passport for damaging probably a 5yr ban from entering the country,