If you're hoping to re-use the stickers, I'm not sure there's a good answer. Heat might be your best option, but be careful -- it's sometimes trivially easy to distort plastics. For example, I couldn't warm up a 5.25" floppy enough to loosen the factory label adhesive without warping the jacket. That's Tyvek, not ABS, but still... perhaps practice on a piece that isn't cosmetically important.
If you don't care about the stickers, just peel off as much of the top layer as you can to expose the paper and adhesive below. Then, I use Goo Gone, but WD40 works also. Let it soak a moment, then rub in a circular pattern with a firm wad of paper towel. Keep at it for a couple minutes and it will start to go. Finish with some fresh liquid and a clean paper towel to remove the last remnants, then clean the oily residue with soap and water, and give it a final scrub with some rubbing alcohol. Good as new.