Google Apps - can be uninstalled and replaced by your own preferred system applications Can we all change the basic system apps installed on our phones? (e.g. contacts, phone, messaging etc.) And replacing it with new applications that can't harm and destroy the phone's stock rom?
Yes, you can... For example QKSMS
for SMS/ MMS, Zero Dialer
for dialer and contact and so on.
These apps can be used without uninstalling the existing default apps.
If you want to completely remove default app then you have to root your phone and use Custom ROM or, customize stock rom.