Drains on blocks look like, and are, just bolts now-a-days, no petcocks any more.
So hard to see for what they are.
Draining the block is really not required for coolant change, owners choice.
After draining via lower rad hose or rad drain, refill with water and warm up engine, set heater to HOT, then drain again, that will dilute old coolant enough as to not effect life of new coolant.
You can use distilled water for this BUT............taste your tap water, if it has no taste then it is OK to use, distilled water is recommended because it has no minerals in it, water with no taste is also mineral free enough to use, but again this is owners choice.
You should stick with silicate based coolant(green, 2 year life) if that is what old coolant is.
If OAT(organic acid) based(red, 5 year life) then stick with that
If you want to change to one from the other then use a HOAT(hybrid organic acid, 5 year life) base for this first change, then one or the other after that.
Back flushing heater core at this time is a good idea to extend its working life.
Google: back flush heater core
Vehicle model isn't important, they all work and back flush the same way
Last edited by RonD; 01-05-2015 at 10:57 AM.