You definitely won't be able to use a password hash as a credential for syncrepl. A hash is a one way function so you can't readily drive the password from it (except via exhaustive brute force).
To avoid storing a clear text password in your config, you'll need to use another mechanism such as GSSAPI. That's what I use in my installations. x509 certificates/keys might be another option.
All of the options are more complicated that using a plain text password, but they're also bit more secure.
Ben