Ok I'll try to take this one step at a time.
yes, you can prepare an SD card. I would suggest finding one with an adapter, or you can buy an adapter separate for about 3$. Vastly improved file transfer speeds compared to the Jetbooks USB cord.
Yes, should be able to use an SDHC card as well, running a 4 gig in my original jetbook.
I "think" it will support up to 32 gig, but thats insanely huge. I've got over 3,000 books on my 4 gig card and I'm using just over 1/4th of it. That being said, I've often seen 4 and 8 gig cards cheaper than 1 and 2's. Depends I think on demand. My wife recently bought an SDHC card and it came with an adapter. Basicly the card slides into a slot on one end, other end is a USB plug. So it turns any SD card into a flashdrive. Very simple, easy to use, and as I said faster transfer speeds.
I would read the manual, the 2 are quite similar, the Jetbook lite is missing a few functions. Like the MP3 player. But otherwise they are almost identical. Be a good way to kill some time while your waiting in my opinion. Also reading all the threads here will both educate you, and forewarn you on do's and don'ts. Like running the batterys down to far may cause a lockup.
I would spend a fair amount of time surfing the project gutenburg or manybooks.net sites. Loads and loads of books there to read. All free, most with your choice of file format. Also don't neglect the upload section here at MR. As to format, many prefer Epub, I'm just as happy with RTF. PDF's are tougher as normally they are formatted for a full sized computer screen. And you have to zoom a lot in order to read them. Which leaves you scrolling up and down for each page.
We were all new here once, so don't sweat the small stuff.
Although you might want to drop the size of your text down a smidge. Seems like your shouting. (probably not how you want to present yourself)
Welcome to MR!