It depends on your exam board, but for AQA, at least, there will be one paper for philosophy of religion and ethics, and another for the study of religion itself. These three themes will often cross over. Ask your future teacher(s) for details on what your exam board will be if you don't already know. When/if you do know, take a look at the specification on the website.
You may find it difficult at times, depending on your ability to apply theory to actual scenarios. You need evaluative and critical skills to do well in the subject.
For AQA component 1, this is what will be assessed:
Section A: Philosophy of religion
Arguments for the existence of God
Evil and suffering
Self and life after death.
Section B: Ethics and religion
Issues of human life and death
Issues of animal life and death
Introduction to meta ethics
Free will and moral responsibility
Bentham and Kant.
AQA component 2:
Section A: Study of religion – for each faith option (2A–2E) the following topics are covered:
Sources of wisdom and authority
Self, death and the afterlife
Good conduct and key moral principles
Expression of religious identity
Religion, gender and sexuality
Religion and science
Religion and secularisation
Religion and religious pluralism.
Section B: The dialogue between philosophy of religion and religion.
How religion is influenced by, and has an influence on philosophy of religion in relation to the issues studied.
Section C: The dialogue between ethical studies and religion.
How religion is influenced by, and has an influence on ethical studies in relation to the issues studied.
Studying for this subject definitely takes time, but if you make consistent bursts of effort throughout the year, you should cope just fine. I made a lot of flashcards and wrote many practice essays for my teachers to mark during the two academic years. This helped a lot.
There are quite a few people who will tell you that philosophy/religious studies is pointless and will not benefit you in the future, which couldn't be further from the truth. I was really interested in everything that was being taught and loved every lesson. Any critical thinking skills you had prior will be further developed. Your writing will be more structured and your expression of ideas will be more coherent. I personally loved learning about applied ethics (very relevant, especially today, with abortion and euthanasia laws, animal rights, etc.) as well as free will and moral responsibility.
I'd recommend watching some videos on these topics by Crash Course Philosophy on YouTube.
If these sorts of issues already intrigue you, I'd recommend it.