There are too many variables to answer that question. The front and side plugs are much easier to access than the rear plugs, and the accessories can make the job take a lot longer. Most garages have a set hourly rate for engine repair, and can provide an estimate for the total cost.
It is impossible to do it you have to pull the engine
to change all freeze plugs on any engine is expensive, as the engine and transmission need to be split to get at pluigs behind flywheel.sometimes the engine needs to be removed freon vehicle to get at others
At minimum, removing the engine mounts is required to access the freeze plugs.
No, it is possible to replace them in vehicle.
engine has to be raise of lowed or sometimes removeing the engine. it better to take to shop.
The heads themselves have NO freeze plugs in them. But the block/engine has 8 freeze plugs in it.
Engine oil is not going to freeze in your engine. It will get very thick but will not freeze.
You still have to remove the transmission on a van to access the rear freeze plugs.
I have never replaced one this model but in order to change a freeze plug you really need to pull the entire engine out and usually many of the accessories on the engine in order to pull it out with a channel lock or similar tool. than simply tap a new freeze plug in.
the best thing to do is to pull out the engine and replace them all with brass freeze plugs because if on fails it will only be a while before you have more, and use antifreeze coolant
With the freeze plug out it will be impossible to keep water and coolant in the engine as it will all leak out through the freeze plug hole. The engine will over heat and self destruct after a while.
Freeze plugs are located in numerous places on the engine block and cylinder head assemblies. Replacement of freeze plugs is usually beyond the skill level of most amateur mechanics.