It will be nice to learn a bit of Linux, just for fun. But you don't need it at all.

I personally don't know how to 'brick' my N800 even if I wanted to. 'To brick' means 'to render permanently inoperative without factory intervention', though some people use it more loosely. Reflashing to get back to square one is common -- I've had to reflash my N800 more than 30 times in the last year, but I'm a pretty adventurous user and don't worry about stuff like knowing what I am doing

Well, I guess that taking a hammer to it (or putting it in the microwave for a long time?) would brick it nicely.

It's an amazing environment, that gets better and more amazing all the time.