you are in for a huge mess, but it is very easy to do.
First get a deck sprayer ($25) and prewet the stuff. Just enough to make the stuff turn dark gray. Do not over do this or you will ruin your drywall.
Then buy a floor tile removal long handled tool. This way you can do the job from the floor and not mess with a ladder. But, be sure and not to gouge the drywall. if you do, just have some tape and bedding on hand.
Just start scraping the stuff off. Use a box cutter to outline the walls so that it does not peel off the texturing from the walls.
Disposal in a heavy trash bag and where ever your city allows you to put it. All it is is paper and glue products.
After it is scraped, be sure and let the walls dry for a couple of days before, I repeat before you begin any new texturing work. This has to dry completely.
Then do any drywall repairs. Then float out the entire area with a light skim coating. Then with your crows foot texturer, do your thing.
Since this is all new, you will have to coat this new area with a special primer before you apply any final coat.