I did what stated in the link and I was wondering if i just have to restart the server for it to take effect or i need to recompile everything in asterisk again?
That is the easiest way. If you have not destroyed the build directory, it will only re-make the files actually needed, and you can manually install just those (probably just main/asterisk).
The neatest way to manually install is to rename them (mv) into place, and then issue a restart command on the Asterisk CLI. That gives minimum down time.
When I modify some of app_xxx.so, or res_xxx.so - I just replace. Then I restart Asterisk. Asterisk must be restarted. Some times, after I replace - asterisk die and I just start it.
When I touch channel.c - then I prefer
make install
And then restart