All tutorials I found were how to fresh install worker MPM + PHP-FPM, since my wordpress blog\'s already up and running with prefork MPM, correct me if I\'m wrong in the simulat
yes, it has to at least replace the httpd process running. you definitely want to test this on a development set up first. it's easy to have a mistake in a config file that takes a while to figure out.
no changes to php, mysql. yes changes to apache httpd.conf to put in worker configurations - they are very different from prefork settings. you need to do these changes yourself in httpd.conf.
no, since this is a php module, whenever php runs it works. that said, it will run one copy for each pool in php-fpm, so if you have multiple domains, you could group them into a pool to share...but be aware of security concerns if you do that.
httpd -V shows "server mpm"
good luck!