How many hours to take apart cooling system?

[generx]

You could probably bang it out in a day, not sure how quickly you work but for an average DIY guy like myself, including a couple of breaks and some goofing off it's taken me about 6+ hours, just be patient refilling the coolant to make sure all the bubbles are out. Mine took less than the manual stated even though I thought I drained it all including from the block. Use distilled water of course.

If you have the "fan tool" or fabricate one yourself, this makes it quick and painless (removing the fan without it can consume precious time) T-stat and pump are super easy to remove since they're right on top, there are 2 threaded holes on each side of the pump which makes it simple to press out with the right sized bolts (13mm if I recall) don't try to hammer or muscle it off.

The old thermostat will likely get destroyed in the process of hose removal depending on miles --those can be a biyatch to take off.

You may also want to replace your AC belt too while you're in there since you'll need to take it off to get the serpentine belt off anyway.