Yes to leaving a step at the bottom of the bore so the sleeve can't drop.
I'd throw the block in the hot tank for about 20 minutes and put the sleeve in the freezer for several hours. Take the block out and as soon as it was dry, drive the sleeve in w/ green loctite/sleevetite. I was concerned about the moisture from it being cold w/ the loctite, but never had an issue. Repaired one really bad 454 chevy block out of a tow truck once that had a huge piece of cylinder wall missing. Concerned enough that I told the owner I'd try it, but if it failed it was his, lol. It ran for several years that I know of after I fixed it.