A few more walls of text...
Thanks for all this! Just downloading the thing you linked me to.
Sorry, this might seem like a stupid thing to say, but what exactly is LaTeX?
That's great!

Just don't let it intimidate you the first time. I talked a friend of mine into changing his 200+ pages dissertation into latex and he wouldn't touch coding html but manages latex fine. Now he won't go back to Word (nothing inherently wrong with Word, but glossing and cross referencing those 220+ examples of his isn't super fun in Word).
Anyway, LaTeX is a typesetting program (or rather, a bunch of macros and a markup language that do just that) so it's quite different from your average WYSIWYG word processor (which is both a frontend - the GUI - and the typesetter in one).
What you are doing when you "write" your document in latex is a bit akin to coding. Don't let that discourage you, though, it's not complex "code". Then you compile/typeset and boom beautiful typography.
Your best bet is to look at a few
basic examples to get a hang on the document structure. Basically you have a
preamble, which is your settings - formatting, fontstyles, packages (extra feature you might want to use), and the
main part, where your content goes.
If you use the included TexShop you can just start writing (well, in latex format that is), whereas other text editors might need some setup or an additional plug in. Though, I'm not a terminal warrior (there are those who use
Vim or
Emacs with latex directly in the terminal - I don't

) nor do I know my way around UNIX and it all went well with TextMate, which also comes with a latex-plugin with syntax coloring and shortcuts.
Reasons for getting a "real" plain text editor is that you can enjoy all their text er... crunching benefits as well as user made shortcuts, color themes that are easier on the eyes and so on. I setup code snippets in TextMate for example so that I just write "ex", press tab and I get the entire structure for an example and that just scratching the surface if you like to automate things.
Since you'll be studying astrophysics I suspect you will also have to parse through huge amounts of data at times. This is where a good text editor will be of great help (I'm a former astrophysics student turned linguist of all things so I've kind of been there, although I've forgotten most of my astronomy studies, sadly -

). Same goes for linguistics and language data in my case.
To use the
xetex engine (unicode and open type support - the latter means you can specify regular .otf typefaces you probably already have) you need this in your preamble, I believe (at least in TextMate, in TexShop just choose xelatex from the drop down menu):
%!TEX TS-program = xelatex
%!TEX encoding = UTF-8 Unicode
Don't forget to try the fontspec package as well!
[EDIT: Just to be clear: xetex is included in that humongous package you downloaded, which byt the way is that big due to all the packages included (extra features, such as glossing packages etc).
You also need to save the document in unicode (utf8).]
Oh, just for the sake of irony: the typeface
consolas comes with all versions of... wait for it ... Office. It's a great monospaced font family for coding. *cough* Actually, version 1.0 is available
here as an exe but
"is only intended for licensed users of Microsoft Visual Studio 2005 or 2008". *cough* Don't shoot the messenger.
By the way if you find that latex isn't for you (but it is!) perhaps
Mellel can provide the comfort of a word processor, while still having a lot of features for those writing academic texts. Bibliography tools come separately (i.e. $$), though Mellel is only $30 for students. I know my university provides EndNote for free to registered students, though. Perhaps there is a similar licensing deal on yours? Quite a while since I've last tried it, however.
Sorry for the walls of text. I might have confused you, rather than actually helping out.
