From what I remember both cowlings are screwed together from the underside, going through the bottom cowling naturally, the top cowling should lift off once all the screws are off. I found the bottom one hardest to get off as it had the column adjusting lever in the way!
Don't know if you can do this with the top cowling still in place but try lifting the felt section at the front of the cluster and it will expose the lower screws that hold the cluster in place. The upper screws are at polar opposites to the lower ones, there's a small plastic piece that's also screwed onto the top section that's there to cover the gap between the cluster top edge and the dashboard's cluster surround, once the top screws are removed this piece just pulls out then it's a bit of fiddling to get the cluster out. Always adjust the steering column as far out and as low as it will go to give maximum menouvering space.
EDIT: There are two extra screws holding on the top cowling (from inside I presume) after remove the three exterior screws from the bottom cowling and removing it. Check this guide on how to do it:
https://www.fiatforum.com/stilo-guides/96473-fitting-new-dials-cluster-gars3.html
Do you think your dad would be interested in a set of manual Abarth clocks?
