@abro,
assalam alikum,
you have plenty of time to prepare for arabic literature provided that you have interest in the subject. i dont know the reasons for changing the subjects but if you find lit interesting then i suggest go for it. i got 120+ in arabic(don't remember the exact)but there are many who hold better than mine . as far as my info, arabic pays you well, especially because examiners presume our incompetence in the subject
now coming to the books. for concept-making the book ive mentioned above is good n comprehensive. other than this you can consult "the arabs in history" by Bernard Lewis(u need to have a taste to read this)
ive heard there is a book by Nicholson which covers quite a lot of the syllabus. check it as well.
in my case, i took advantage of the arabic sites only. all i had was the Zayyat's book n lewis with a vvery limited time at my disposal.
best of luck. im sure you can do well in it
p.s: creativity and interest in any subject can lead u to success