How to uninstall Git from the command shell?
Do not uninstall Apple-distributed Git. You can leave it as it is and run another version by having it in a directory earlier in PATH environment variable.

The easiest way to install another version on OS X would be to use Homebrew packet manager.

After installing it, you can run:

brew install git


Homebrew (brew) will take care of all dependencies and configure the latest Git version, however there is still a chance it will find a setting it cannot resolve automatically, so read what Homebrew says at the end.

Packages installed with brew do not interfere with system-preinstalled packages.
It installs packages under /usr/local/Cellar directory and puts executables in /usr/local/bin, so you just have to keep it in PATH variable in before /usr/bin.