installing thermostat

[sd88supra]

my car is running hot again, and given that ive installed a new electric fan, new water pump, tightened my belts and got a block test (no bhg), i have yet to change the thermostat, so im guessing this is my problem. it takes a while to get hot, but even with the fan on and it being pretty cool outside the gauge goes up to red. right after hitting red and accelerating, the needle drops quickly. my guess is the coolant isnt flowing as it should due to a bad thermostat. i got a new one and will replace it tonight under artificial lighting lol. i do however have 2 questions regarding installing a new thermostat.

1. do you really have to drain the coolant prior to removing the old one? im guessing some would spill but i suppose you could just refill whatever fell out (and of course being carefull

2. i got a 180? thermostat, but whats the deal with people drilling holes in theirs? and whats the deal with a brand new thermostat not opening up when first installed? is there anything i should do to it? im guessing these leave the manufacturer ready to be installed but ill let the supra experts guide me. thanks in advance.