Took the new Uberti to the range today to determine the correct front sight height because the factory front is way too short. So I made this adjustable front blade (see photo) substitute to get a good elevation zero. That worked out to be .483 overall height. Now I know what after market size I need.

However, I think the trigger return spring broke because the trigger just wiggles back and forth, and it did not do that before.  Luckily, the rifle still fires. Is this a part I can replace myself?

No, not at all. Out of the box, it was a heavy single stage. The change happened today on the range.

Thanks Howlin, good to hear. Funny though that it took about 80 rounds for this the trigger to loosen as, it was tight out of the box.

(Edited 3/9/21 to correct overall  front sight post height to .480") My height determinator (see above) measured .480" with my 250gr. XTP/7.3gr. of Unique handloads at 25 and 50 yards with the rear sight slider between slots 2 and 3.
Luckily, I had this Lyman 31 VA front sight i my "stuff drawer" from where I don't remember, but it was about the height I needed and appeared to have potential in The Uberti's dovetail slot.
The Uberti's dovetail slot is not apparently tapered from one side to the other like I have found on every gun I have owned in 60 years, so maybe that's why they use a set screw to hold the front sight (and rear) in place.
I mated the Lyman to the barrel dovetail by simply drawing the bottom surface of the sight's dovetail across a file held flat on my bench. Then reversing the sight in my fingers and drawing it towards me again to keep the material removal as even as my hand hold allowed. I dragged the sight sideways because it was easier to hold it steady that way with my fingers.
Just a few "draws" were required before the sight could be pushed in by hand about half-way right-to-left, and in fact at this point you could still read the "31 VA" stamped on the bottom of the Lyman. A brass drift did the rest with the barrel held steady in a padded vice and it seems very secure, so I think the Lyman had a normal taper to it.
Photo shows the finished product centered by eyeball. Tomorrow at the range we will see what there is to see...
It may not be too pretty or authentic, but then I have not taken a file to it yet.

New front sight worked very well for me at 50 and 25 yards:

Did not know that. I wonder how difficult it was to come up with a tiny (and strong) flat blade screw driver back in the day...

With more shooting, I ended up with a Marble front a bit lower than the Lyman:

Fitting it to the Uberti's dovetail slot only required dragging it across a good file like this. The shape of the post makes it easy to hold straight, and to reverse it from left side to right side every two draws:

Thanks Sgt, not worried about it anymore.