I have no clue about the directed readings as my school doesn't have anything like that, but I don't know why they would have to be an expert, really. But if you get to write a lit review (that could be possibly published) and you have the opportunity you should seriously consider taking advantage of both these opportunities. The results of these opportunities would look really good as a writing sample or possible publication/ poster on your CV. If they had such a thing at my school I'd be all over it.
I wrote my manuscript/proposal the previous semester during my research design course and conducted it during my independent research the next semester. Having the majority of the manuscript written was pretty much a must. During the first to third week (at my school at least) you send the IRB application, that takes a few weeks, then you start collecting data. Since you can use rats and thus have an easier time gathering enough data I imagine it would not take you until the end of the semester to start analyses and finishing your manuscript. For me 2 weeks before finals we ran the analyses and I turned in my completed (and mostly revised by my professor) manuscript on the very last day of the semester. My manuscript is definitely worth the time commitment as I could make multiple poster presentations out of it and a publication if I so wanted. Not to mention how awesome something like this looks on your CV.
I would ask the professor you would be working with how long it would take you to gather the data for the experiment you have in mind. If it won't take long (and your school will allow this) you could write the proposal, conduct the experiment, run the analyses, and finish the manuscript in a semester if you hustle. Otherwise it is almost mandatory that you complete your proposal beforehand (i.e., during the summer). I don't know if you've written anything like a manuscript before but in case you haven't you should realize it could take a good month of straight writing and revision to get it to a presentable level. I would send my sections to my professor who would edit it and then I would edit it again. My manuscript (minus the pages of measures) is a full 26 pages. I'm sure you can imagine how long that took considering the process my professor and I used. And that, I believe, is short for a manuscript.
Overall, I do believe that a semester is long enough to produce a quality manuscript. If your up to such a challenge its totally worth it. That's my dos pennies. 🙂