The PP site has a main menu that goes across the page under the title. My menu is located in the upper right corner and is vertical, not horizontal. How do I make mine look like hers? Is this a CSS thing or can I easily fix this?

That's a bit more advanced and it's the only thing so far you've asked about that needs CSS. Here's a few past forum links where someone has asked the same questions and the answers have been posted:

• http://en.forums.wordpress.com/topic/enlarging-your-header-image-in-imbalance2?replies=4#post-790098
• http://en.forums.wordpress.com/topic/align-menu-tabs-side-by-side-in-imbalance?replies=22#post-764995

How does she get all the “extra stuff” (e.g., categories, blogs she follows, archives) to show up at the bottom of the homepage? On my page, some of this stuff is up at the top of the page and you have to scroll way down to start seeing blog posts. How can I “flip” this?

The categories, archives and list of blogs on that blog are setup as footer widgets. You can go to Appearance → Widgets and drag the ones you want into the footer widget areas on the right. Here is a related help page about how widgets work:
http://en.support.wordpress.com/widgets/

The PP site has four columns, my site has 5…how do I get my site to have 4 columns across? Or, am I misunderstanding what a column is?

I think you have the right idea about what a column is. Imbalance 2 can have a fixed or fluid layout. A fixed layout means the container is a fixed size (the 4 columns example) and a fluid layout makes the container change size depending on the browser width so it can have more than 4 columns. To change that particular thing, no CSS is needed. Just go to Appearance → Theme Options and change the "Enable fluid grid layout" setting to no.

For example, I’m not totally sure what menus are and do. I’m not sure how I get pages to work or what the difference is between categories and tagging, thus, it's hard to ask the right questions.

For those kinds of things, there are several really great help pages that I bet if you searched at http://support.wordpress.com/ you would find a lot of what you're looking for. Here are some relevant links for the things you've mentioned. Most have screenshots and some have videos which I think are really helpful.
http://en.support.wordpress.com/menus/
http://en.support.wordpress.com/post-vs-page/
http://en.support.wordpress.com/posts/categories-vs-tags/#video

I’m not totally sure what menus are and do.

Please read this section Using WordPress.com to Create a Website http://en.support.wordpress.com/using-wordpress-to-create-a-website/
http://en.support.wordpress.com/menus/
There are many common errors, misunderstanding and misconceptions when creating custom menus and you can read about them here > http://wpbtips.wordpress.com/2011/12/19/custom-menus/

I’ve found a site whose look I really like: The Patterned Plate: http://thepatternedplate.wordpress.com/

The author has requested that people do not contact her about her formatting. She does note that she uses CSS. I have purchased CSS, but I’m not sure what to use it for. For example, some of the changes I want to make might be part of my template, Imbalance 2, but I don’t know how to figure that out.

Here are some of my questions:

The PP site has four columns, my site has 5…how do I get my site to have 4 columns across? Or, am I misunderstanding what a column is? In PP, she has four postings going across the page. I consider these to be columns. Am I right about that?

How does she get all the “extra stuff” (e.g., categories, blogs she follows, archives) to show up at the bottom of the homepage? On my page, some of this stuff is up at the top of the page and you have to scroll way down to start seeing blog posts. How can I “flip” this?

The PP site has a main menu that goes across the page under the title. My menu is located in the upper right corner and is vertical, not horizontal. How do I make mine look like hers? Is this a CSS thing or can I easily fix this?

There are also some nice ones that allow you to spotlight current posts from certain categories on the main page.

In general though, I tend to stay with the clean and simple. I've gone to a theme that shows two columns of posts (Inuit Types Standard) which allows me to display a good number of posts without having an overly long main blog page.

Still, I would say that some more flexible multi-column themes are needed. I may not use them, but there are those out there that they would serve well.

Hallluke - I've been looking for them, but it came up with bupkis.

lh

I've always wondered why someone gifted with CSS doesn't start a "premium WP.com Sandbox Skins" service. They could certainly get money for it.

What would be great is a four (or more!) column theme for wordpress.com where you could display multiple posts side-by-side, especially for blogs like mine that focus on current events, politics, and the like. It would also be great to be able to configure the layout a bit more, so that I could keep posts that are drawing eyes up front, while letting less-successful efforts fall off the "front page" so to speak. What I'm looking for, in short, is more newspaper-like formats.

There are a bunch of really great, crisp, and uncomplicated four+ column themes that could fill this role:
1. News Print - http://www.theenglishguy.co.uk/news-print-v20-theme/
Very simple look, allows 3 or 4 columns, and allows you to configure the layout.
2. Blog Times - http://wp2.milo317.com/
Based on the New York Times' classic look, allowing you to place multiple posts the way you want them.
3. New Yorker - http://www.wplocker.com/premium-themes/stylewp/the-new-yorker-premium-wordpress-theme/
Likewise based on the magazine, allows for a lot of customization, and display of many different posts at
once without overwhelming the eye.
4. NYC Reds - http://3oneseven.com/02/nyc-reds-wp-theme/
Similar kind of thing, but a bit less obviously newspapery and a bit more color.

A straight copy of one of these themes isn't strictly necessary, but it would be nice to have something along these lines if it's possible.