Contacts.apk questions

[pathfin9]

Hi,
I'm fairly new to rooting, and I wanted to only change my Contacts.apk file.
I was able to get it to change to one theme that was just a lone Contacts.apk file, but if I try to take a Contacts.apk file from another ROM and try to install it it doesnt work, and renders the phone function unusable.
I used Terminal Emulator to install the Contacts.apk that actually worked.

Any ideas on how to do this, or where to find single Contacts.apk files?

Any help would be greatly appreciated, as I have been searching for days with no luck finding any, except for 1.

Thanks!

-John