If you're not experienced with Linux, you should probably use RPM's. As you get more experienced, you can think about compiling them to get more options. The MySQL RPM's are available directly from the MySQL website:
http://www.mysql.com
And Troels Arvin has kindly donated his time to creating PHP RPM's and modules:
http://rpms.arvin.dk/php/
Apache is also available via RPM, of course, and should be preinstalled on RH7. If not, you'll find it on the CD, or on their website.
Using the RPM's, you should be able to start tinkering with them as soon as they're all installed.