Short Knife,
Your friend needs to identify which model type #3 American he has. Photos will help?
Type I uses a stud on the hammer to actuate the bolt stop. There would be a return spring for the bolt stop, but I don't know where this would be located. I don't have that type to compare. Parts maybe difficult to find for this type.
Type II uses the trigger actuated bolt stop. This becomes pretty much standard for the #3's, but may not be interchangeable with all models. It's return spring is located on the front inside of the trigger guard. If the bolt stop is not working it is because the spring is either broken or cracked. (the Uberti repro bolt stop spring may be made to work.)
The hammer not staying in full cock will be either the trigger sear is damaged or the full cock notch on the hammer is damaged, or perhaps a bit of both.
These parts maybe difficult to find as well. However, they maybe repaired with welding.
Hope this helps.
My best,
Blair