coolant change 190 general questions

[tunk]

Here's what I gather from my haynes manual and searching the site, couple of questions at the end.

Protocol:

With cool engine, open rad drain at bottom, drain fluid. Open engine plugs drain here as well.

Fill through expansion tank with hose water.

Run engine with expansion tank cap off until engine goes to first temp reading all the while adding water as needed with heat on full. When first bar is reached put cap back on and run engine for two more minutes.

Drain system as described and refill cool engine with proper mixture of antifreeze and distilled water.

Couple of questions: from searching on this it seems like there is a major concern that cool antifreeze will come in contact with a hot engine block and that it will do big damage. How exactly is this avoided, my impression is that as long as the engine is allowed to completely cool between flushing and draining that there should not be a problem… I don’t know and need to know what you could do to screw the process up and cause major damage. Secondly, I plan on changing the thermostat as a preventative measure. Is there anything else that I should swap just as a throw away part on a car with 190k (when doing this for the first time in who knows how long. Certainly not since I got the car two years ago I know that much). Third, there was also this issue that I saw when searching that said you can introduce air pockets into cooling system if things are done improperly so how exactly is this avoided. Lastly what does heat on high mean? Is that just highest temp highest fan setting or do I need to throw on the defroster or something else in addition?

Thanks for the help,
CDT