Bad character data

I posted this to the pgsql general list, but alas, I did not get any
responses. Perhaps someone here could be of assistance?

I have a database with some bad characters in it -- some users had entered
MS Word smart quotes, em dashes, foreign characters, and they look like
gibberish coming out of the database. Most important are the smart quotes I
guess.

What's the best way to replace these characters? I thought I might be able
to run a simple SQL UPDATE command, but some of the gibberish for different
characters looks the same (at least from my client it does), and it would
clobber them all.

I have a feeling there's some sort of ASCII code or unicode solution to this
problem, but I could use am little push in the right direction.

Thanks.

Noah.