I cannot possibly say how much work will be required – it depends on how easy or how difficult you find the syllabus.
There is absolutely no way that you can pass the exam by only working through exam questions (the ACCA does not release past exam questions for Paper F3 anyway!).
You should watch the free lectures (with the lecture notes in front of you), and you should buy a Revision Kit from one of the ACCA approved publishers and attempt all of the questions in it.