The above video goes away if you are a member and logged in, so log in now!
Don't modify the switch in the back, it works with dangerous live voltage! A lawn mower/car/PC switch is definitely not safe for use with live line voltage - using them is asking to get shocked. What I would do is connect the switch to cut the connection to the front panel (reset) switch (it works safely with low voltages), though it would probably mean cutting a trace on the mainboard, because you can't solder anything on the flat reset cable.
Any switch that is rated for 120V at whatever amperage is going through the switch will be fine (hell you can use a light switch if you like). 120 is not dangerous live voltage unless you are playing with it hot and careless. As with ANY electricity you want to make sure you don't have any shorts when you are done as to not cause damage to the unit. Also, you should always have the unit powered off and unplugged when working on it.
Yep. A 120V/230V (whichever your country has) rated switch is ok, as long as all connections are kept away from the low voltage side (mainboard etc.) and should be insulated well (maybe I'm being too careful, but I've seen some scary stuff in devices people have modified). I just haven't seen many mains rated key switches around for a reasonable price.