macOS Replace a file in an Existing Package?

[pilotError]

Is there an easy way to replace a file in an existing package without having to unpack / repack the entire package?

I have a Modified .plist file that I would like to just put back into the original package. I don't have the original directories around, and I'm just too damn lazy tonight to unpack the thing and repackage it.

 

[pilotError]

Nevermind, had trouble finding the flat package editor at first...

Forgot they hid it under the packagemaker utility.

One more question, which compression format is the Payload in?

Do I gzip then compress??? It's been a while...