\openg in MinionPro (from Acrobat 9)

OK, by some research I could answer both questions myself:

1. A table of glyphs in a (PFB) font is produced by the command t1testpage FONT.pfb > output.ps, producing a PostScript document. By doing so with MinionPro-It.pfb, I found the \openg symbol as uni0434.ital in the output file.
2. Replacing /afii10069.ital by /uni0434.ital in base-MinionPro-ab.enc made \openg work again.

See this question. The encodings have changed. The MinionPro package has not been officially updated for some time, but there are unofficial updated encodings here.