1 i assume you're doing a firware flash, so most likely not. the worst that can happen would mess up your dvd drive (assuming of course that the modder knows what he is doing)
2 never done it, i like live too much
3 not sure, should be compatible with most.
4 probably different experience levels, though i'd say it takes about 20mins. it needs to be disassembled and flashed, taking the casing off, with the right tools, takes around 10 mins alone. So the 10 min estimate could be the flashing itself.
5 it will be able to play live... until an update is released. after that, you'll probably be banned.
6 i've modded a few consoles for friends, i considered having this done myself, then i opted out because i spent way too much money on my 360, accessories, games, and custom casing for a ban. :disagree: