scraping the popcorn off isn't hard, just really messy. If you are replacing all carpet, pretty easy. If you need to keep carpet or hardwoods/tile, get a big roll of visqueen (plastic) and tape it up the walls about 3 feet all around before you get started.
You will need a sprayer (like a 3 gallon fertilizer sprayer). Secret is to use downey fabric softener 1 cup per gallon mixture. You'll need a respirator or breather, cause it is smelly.
Spray the ceiling liberally, wait for several minutes for it to sink in, then take a big sheetrock scraper and it comes right off. You might have to spray a couple of times if really thick.
when done, you can just roll up all the visqueen and old mud and chuck it.
Be forewarned, many spray because it is cheaper and it covers up all the bad sheetrock work. You will probably have to float out the ceilings if you are going to do flat or custom texture. I hand stomped the whole house when we moved out here. Flew my bro-in-law who is a sheetrock guy out for a week and we knocked it out before moving in.