In WordPress, themes are developed using a mixture of CSS, HTML, and PHP.
Try pulling down some of the settings menus along the left side of WP-Admin and see if you can't find anything. Plugins are allowed to add themselves to the menus, so start by looking for a relevant option that wasn't there before. The plugin may also link to its settings from the Plugins page, so you should look there as well. Go back and review the screenshots as well and see if you can't figure out if there's another way to get to them highlighted.
I'd also recommend that you install/keep a minimum number of plugins required to get the desired effects you want; large numbers of plugins have the potential to make things slower both on the server end and for the end-user (your readers) as well as providing a number of easily-accessible targets for hackers/spammers. And I don't want to be mean, but you shouldn't be modifying the plugins at all unless you know exactly what you're doing to them.
The process of switching isn't too complicated, although they have the export/upload system set up really poorly. I have too many posts for them to all be uploaded at once. I had to manually export my site in chunks, which was a big headache since the date system is all whacky.
Anyway, .org is legit. It allows you to do so much more. It is a bit more complicated, but it's nothing you can't get the hang of relatively quickly.
Actually, if you're talking about any file size limitations, those are PHP settings decided upon and set by your webhost. If you manage the server, you can temporarily bump the value to something bigger, but if you're paying for hosting somewhere this is almost guaranteed to be outside your control.
You can get around this, however. Try GZipping (not plain ZIP, your file should have a .gz extension) your WXR XML file and uploading that. If you still can't get anywhere, you can try this utility, which will automatically break your WXR into smaller pieces that you can then import. Yeah, it might get tedious, but it works. (Relevant Documentation)
I use wordpress but haven't quite figured out everything though. it's not quite the same as blogger where you can tweak it to look exactly as you want. still working on it though......