How should I format code words in my personal statement? I'm applying to Master's programs for Statistics. In my personal statement, I mention the names of some R packages like car, ggvis, and effects when I talk about professors that I would be interested in working with and some of my own research. Typically when people write about these, they are just all lowercase letters, not italicized or anything.

It looks really weird in a regular Word document, especially since "car" and "effects" are regular words. I'm afraid that it may look out of place. Is it okay if I change the font to the code font so it looks like ggvis and effects? I wouldn't use the grey background, but the serif typewriter font is pretty standard for bits of code, right? I'm afraid it will look unprofessional for academic/business writing.
Probably you are thinking about this too hard: as long as it's clear what you're saying and choosing a reasonable form of presentation, it's probably fine.  Monospace font is one way to do this, another way is to put the names in quotes, just like you did in your question.

If you want to be really cautious, you can look at scientific papers from the field and see what conventions people tend to use.  That way, you will be certain that your readers will find your presentation familiar.