"How much will it cost to change antifreeze?" What are you changing antifreeze in, a small car, large truck, D-12 dozer, mining truck??? Reason being, small 4 cylinder engines take less than a engine that is 8 cylinder, and a 10 cylinder engines takes even more. Look in the owners manual of the vehicle you are wanting to change antifreeze in and it will tell you what the fluid specs are. If you don't have the owners manual, go on line and you can find it, or call a local auto parts store and they to can tell you.

Depends on which antifreeze you use. If you use the common ethylene glycol that is toxic and lethal which will kill anything that tastes just a small amount, ie. fish in the downstream from your house or a pet or any animal that is thirsty, OR use Propylene Glycol that last longer, is more effective and is not lethal or toxic but costs a bit more initially.

A system flush will vary by shop, but expect $80 +

A few years ago, A local car shop which has already closed quoted me a price of $160 so I declined, he then offered to do it for $80.

In most cars you can do it yourself for under $20.