First of all, depending on your distro/environment, the module may be available as an extension DLL/Linux package which is much easier to install, and doesn't require any recompilation. However, if you absolutely have to...
1 - Yes, generally you'll need to specify everything from the initial build. Unless you want to radically change the setup you have (ie remove modules etc)
2 - Create a php file with the following in:
View this script in a browser to see information about your current installation of PHP. At the top you should see the configure command used in the initial build. Note that the paths of some libraries may be different on your machine, if you haven't compiled before (eg paths used during compilation by your favourite distro people).
3 - Yes, generally you'll need to do ./configure [options] && make && make install to get the binaries and modules in the correct places with the configuration options you supplied.