terminology question - upgrading one port with another

[Jim]

I'm trying to update something (actually install KDE4), and In need to
make an 'update chain', but I can't remember the proper term. Namely I
have port found in 'foo/abc' (abc-12345) and want to replace it with
'var/xyz'. I know there are several ways to do this (one involving
entries in a file in etc?), but I cannot come up with the proper terms
to find what I'm looking for in a search?

Can anyone tell me a few terms that might help with this one? I've
tried compbinations of "port", "upgrade", "search" and "different",
but that (unsurprisingly) isn't getting anywhere.

Thanks,
-Jim Stapleton