It would great if more nursing programs could open their clinicals to re-entry nurses! The re-entry program I took only had a couple of weeks of clinical. I could have used a couple of months! I'd imagine most nursing programs won't allow re-entry students as they're already full up with their own students but it's certainly worth looking into because if you got lucky and could do that, that would be a great way to get back in to the swing of things.
However, twenty years is a long time to be out of the field. So many changes, you really would be starting all over in many respects. And here something else to consider. Are you thinking of returning to nursing because it sounds exciting, challenging, and rewarding or because that's what you were trained for back when and it pays pretty well?
Personally, I've found that clinical nursing isn't my passion. I look for jobs where familiarity with medical terminology
and the health care system is useful (vs. clinical experience). The pay is considerably less than nursing positions but it's considerably more than the craft store - though if the craft store does pay well enough, why not? What fun!