I am working as a research assistant for a professor and I was hired to write a literature review on a rather broad topic that is well outside of my knowledge domain. I am concerned that i'll most likely create a bad product because I don't have a crystal clear idea as to what it is I am intending to search for, I only have an approximate idea. It seems sort of strange that I would be hired to write a LR on a topic for somebody else and I am wondering if this is a common occurrence? Do professors typically hire students write the literature reviews for them?
I don't know how common/typical it is, but it seems to be certainly part of a job description for a RA, especially if your implication is that you are a doctoral student.
One reason for it is just part of your training and when it comes time to do your own dissertation the practice would help.
But additionally, if the professor is exploring some new research direction it would be helpful to them to have help in assuring that they don't miss something important.
And anyone starting out in a new research area will have the same dilemma as yourself. It is hard to know where to look initially. You need to review a lot of papers and chase a lot of references. That is the nature of the task.
If it were crystal clear it probably wouldn't be necessary.
It is good that you are humble at the start. I'd guess that the professor knows that it isn't easy and that the initial product might require refinement. Just be honest along the way about what you have "covered" and any gaps you think might still exist.
I have hired a master's student to work with me on a literature review in the past on a topic that she initially knew little about. I cannot assume that your professor's situation was the same as mine, but in my case, my purpose was to use her services to do a lot of the legwork in the mechanics of identifying literature and related resources. When it came to the actual reading an meaningful analysis of the articles, I did almost all of that myself. The student saved me a huge amount of time; I could not have produced the eventual reviews in the time I did without her help.
On her part, she learnt a lot about new topics and she eventually coauthored on a very highly cited article. So, I believe that intellectually, the experience was very helpful for her as well. (Even now that she has since become a professor, that remains by far her more highly cited work.)
So, there is one anecdote at least of how such an experience might be valuable to both the research assistant and the professor.
I have not done so, but I have asked masters students hired as RAs to do so, for grants. Results have varied between good and useless. (I wound up entirely rewriting one, cursing the whole time at their failure to synthesize the results from findings). Regardless, a lot got done that I didn't have to do, and could build on. The best part produced was the annotated bibliography--abstract, link, and their comments on each book/article/paper.
Google Scholar is your ace. Google the topic, google the names of the people involved. Copy-paste the abstracts into a word document, rewrite them in consistent tense and structure so it presents a summary of the articles. Read the conclusion for articles with 'teaser' abstracts and add that to the summary. Make sure each summary includes the research question/hypothesis, the methods used, and the findings. Keep an exact bibliography, and a file with all the articles used. Do this for a page, present the result to the professor, get feedback, continue.