Wrath of the Lich King download help.

Hello!
I was wondering if I had to download bittorrent to download the WotLK client in order to play the new Lordaeron server. I've downloaded Cata, Vanilla, and MoP without using bittorent what makes WotLK any different?

Warmanes official download links are torrents. There is nothing different that forces you to use torrent to download wotlk client but you would have to find direct download of wotlk client elsewhere. Cata and MoP are able to download content while playing so there are minimal clients available on forum, which doesn't involve torrents. Wotlk doesn't support that so you need full client to play.

So, I have to download bittorent correct? and I need a cofirmation that this is 100% safe.

I would suggest using qBittorrent as torrent client since it doesn't try to trick you into installing additional software. That and the torrent from download page are free of viruses. If you are worried about legal safety it depends on your country. In some countries you can get warnings for that.