Yes, you probably do need an accountant. Personal SA tax returns are relatively easy if you do a bit of research, but a limited company is a whole different ballgame, such as running your own payroll, company accounts have to be drawn up according to company law and accounting standards and require a balance sheet, corporation tax returns are different to personal SA returns, etc. Some people do their own, but most don't.
You need to plan things better, i.e. need accounts to support dividends, need to get the right mix of dividends/salary, need to understand the different rules for claiming expenses, understand benefits in kind especially re vehicles, etc.
I'd say anyone with profits more than the average income, say £26k would still benefit from being a limited company, even factoring in the accountancy charges (rule of thumb about £1,000), but the savings are more if profits are higher. You can also benefit by involving other family members, such as a wage to your spouse or issue shares to them so they get dividends too, potentially using their dividend allowance and basic rate band.
Of course, it's not all about money, being limited may give you a better profile for prospective customers and you may feel more comfortable with the limited liability which can protect you if things go wrong.
A lot to learn and understand. A good accountant is worth their weight in gold. But, if you have the time and inclination, plenty of googling could mean you may be able to do it yourself, but the risk is that you don't get it right and fall into some of the many taxtraps.