cant get coolant drain bolt off
 

my sis just got herself a used 94 Accord auto with about 240,000km, it overheated a bit the other day after i noticed it was really low on coolant, the coolant was filthy by the way, anyway, im about to change it but i cant get the drain bolt off the engine block, ive removed the one from the bottom of the radiator but the one on the engine is soo tight the nuts begining to strip, do i have to worry about removing the nut? will most of the coolant be drained from the radiator and reserve tank anyway? thanks guys

not all gets drained thru the bottom rad tank plug, take your water hose after draining the coolent and allow the water to drain thru the engine and drain out the rad bottom drain. This should dilute most of the fluid out. Also take the rad out if you can and drain it backwards, or do a reverse flush if you have an air compressor from the bottom up to clear the upper core of junk. disconnect the top rad hose to drain out, not back into the block. don't overpressure the rad.