a PCV valve is a ventilation system for exhaust gases that sneak into the crank case, basically. if you're looking at your engine from the front, it will be on the passenger size, near the top of the UIM (black snail looking thing). overtime they can get a little clogged and prevent MPGs and if bad enough can cause minor oil leaks. it's like what, $3 for a new pcv valve??
and as far as coolant, just pop off the lower radiator hose, drain it out, and just flush it with water, and when you're comfortable with it, just put your coolant back in
but if you're really concerned, it's okay to get the whole block flushed out professionally, it can never hurt. but i understand you're short on cash (like me) so i figured i'd give you the DIY option.