1. Chances of you bricking your wii completely relies on you and your willingness to learn about the modchip industry. It's basically self-inflicted, if done improperly.
2. You brick it by updating the actual firmware of your Wii Console to another region. For example, appying a NTSC system update on a PAL Wii console.
3. Currently, there is a 70% of imported games working, same region games regardless of country release works at 100%.
4.Once you download a game (if you would, lol), you could use any burning software that supports the *.iso files. Several people prefer to use ImgBurn, I personally just use whatever software I got lying around. It works all the same.
5.Yes, you gotta always gotta keep up to date if you want to make sure that console (after being modded) is safe and trouble free. You have to apply wiikey updates (if there are any available at the time), also you might want to use brickblocker and region frii in some instances when (or should I say if) you are burning iso game files.
If the console's main purpose (after chip installation) is to play a majority of NTSC games, be prepared to accept that if your console is a PAL region that it may not play ALL games but MOST. And the chances of you bricking your wii using NTSC region games on a PAL region games are high, especially if you do not take the necessary precautions. My intentions are not to scare you as I found myself in the same predicament when I initially got my console chipped.