Welcome to the forum.
If it were mine I'd change only what is required to make it roadworthy, once restored it won't really feel like the same bike.
I wonder how many forum members still have their first bike.
I still have my first road bike, a 2003 Jincheng M50D (Z50 copy), it's rough but it's still in use.
My first bike used off road was a PC50, 76 I think, it was sold to a mate for £40 many years ago.