WoW Account questions (please answer)

Well I decided I would get WoW. But there are a lot of questions I'd like to ask.

So, currently I am playing on a trial account. And I already created an account in the website. Once my trial is up, I am pretty sure like most trials, something will pop up saying "Buy Warcraft now or Enter Code." So, once my trial ends, what should I do? I am planning to pay by prepaid cards. And my friend said I don't have to download WoW anymore, meaning I don't have to spend 40$$ on WoW, and just to spend on the prepaid cards. But the thing is, I'm not sure my trial version downloaded all of the stuff. So I really need help..

Really?
I would go with the downloaded version.
Trials normally don't have everything, but they can. But I wouldn't take the risk.
Wouldn't you want a horse with a saddle and not just a horse?

So what are you suggesting? Buy the game at my local game store? Because I heard I could download WoW: Burning Crusade at WorldofWarcraft.com

I would buy the game at your local game store.

You have to buy a cd key before you can play WoW with a subccription. You can either buy the cd keys from the website and install it from there or from the store. I think they are the same price, not sure.

But, yes you have to buy WoW still you can't get a subscription without buying the game in some way.

Well, even you try register with another subscription that won't work if you don't have bought the game. You need to buy the real game so you can play :)

When ever you download the trial version you download it all but can't get past level 20 so that 40$ can be used for some game cards.