Hiya mate, I think its all or nothing !!
You either rebuild it completely or leave it as it is, I have a mate that is besotted by a diana 22 he had as a kid, And spends time & money on it ! Which is OK of course ( Nostalgia is not what it used to be Ha ha, )
I know you didn,t ask value, But I had these for sale a year or 2 ago-
A Diana 22, A Webley junior & a Original 23 £40 each for the former 2, & £50 for the Original ( Only silly offers )
The Diana/ Original 23 ( As you said ) has a rifled, Solid barrel & is a nice gun,
I like them, but only some provenance would make me refurbish one !
You will never get your money back, Ged.