Morning Winmag, the Numrich Arms schematics can be a lifesaver when that little part goes missing. The P-38 is quite a nice shooting sidearm, the fact your father got it makes it twice as valuable imho. Hope you found the parts you needed.
The P38 still has all the original parts, although I ordered a few tiny springs (and a new top cover) from Numrich just in case. And a Wolff spring kit as more just-in-case.