...
> PageFrame subclass and usually names are
> this.PageFrame1.Page1
> this.PageFrame1.Page2
>
> I decided to change this PageFrame subclass and make
> MemberClass non-empty containing subclassed Page which is
> named let's say MyPage ( surely I cannot name it as a base
> class Page again ).

I think you actually could continue using the old names, although I agree that self-explaining names might be easier to read and maintain.

> I am trouble now with this project because
> neither "Gofish" from download section nor "Tools/Code references/replace"
> are able to change all occurences of
> "PageFrame1.Page" to "PageFrame1.MyPage" in a project in a code and
> properties.
>
> Any ideas would it be possible somehow overcome that and make the global
> replacement? Or it would be better to keep this project as it is

You could make an own tool / code for that particular scenario.
Maybe (make a few backups first and then) do something like

FOR EACH oFile IN _vfp.ActiveProject.Files
    IF INLIST(oFile.Type, 'V','K') && forms and vcx-libs only
        USE (oFile.Name)
        REPLACE ALL methods WITH STRTRAN(....) FOR ... etc.

hth
-Stefan