Heya @Matt, your Transformer can certainly take 4.4 as it is not that old. The only thing is there could be some hardware standards for new features that your tablet doesn't have (like graphics that are beyond your GPU for example), but this won't stop your tablet from taking 4.4
To answer your other questions, root is super simple, here's a link to a one click root tool from XDA Developers
. it tells you what to do (basically download and click Root!). I haven't used it so I can't vouch for its quality, but getting root is pretty simple so I see now reason why it wouldn't work.
There's a lot of different degrees of bricking, soft bricking is relatively easy to fix but there's no simple way to do it, it kind of requires some experience and lots of attempts. We sometimes have editors spending half a day unbricking a device here. So follow all steps to a letter when flashing custom ROMs, ensure you have the appropriate firmware for your device and read as much as you can first to ensure you don't make any silly mistakes that others have warned about in comments etc.