I converted to the Arrow IV last January (lots of Warrior time and a bit of Cherokee time before, like you).
The retractible gear is pretty simple and obvious. Constant speed prop makes very little difference in the cruise, and it's just a few extra procedures to learn for approach and departure. Really no problem at all.
The biggest problem I had was the downwind leg. There are a few extra checks to do (gear down, set the prop speed, check the gear really is down) and less time to do them because you're going a little bit faster. For the first couple of hours, I was always behind the 'plane on downwind. All it took was practice, practice, practice....
Good luck - seems like you've got a good day for it, too!
FFF
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