Apparently somewhere there is a reference to msql.so that should
probably be mysql.so. Usually when there's a bad reference in the
httpd.conf file apache will fail to start.
Also, there's 2 versions of PHP running on your 550. One is for the
admin server the other is for the virtual sites. Make sure you've got
the right php.ini.
There's really not much to the PHP upgrade. There's a package that will
do it on the virtual host side. (The admin server will still run the
original version.) There's some pretty serious problems with the version
of PHP that you've got now. Edison makes a good package that does this.