To make the new apache run on startup, I'm assuming you used the default directory of /usr/local/apache2.
(I don't think this is the correct way to do things, but it works)
go to /etc/rc.d/init.d/httpd
this is the conf file for the services at startup
scroll down and see
I simply took those two and made them
(I'm not too sure what the HTTPD thing is, but my apache seems to work without it)
Now whenever you go to serviceconf, the httpd service directs to your new Apache installation.
And so far, the first apache install from Redhat hasn't had any effect on my current apache. Have fun