I ran the Tomcat installer from Layer1 as well, and apache was wouldn't start for me either. After reading this post (and a couple of others), I uncommented that line as mentioned above and I also had to uncomment the &AddModule mod_jk.c& line to get apache to start again. Then I enabled one of my domain names with JSP from the WHM and loaded a simple .jsp file to test it... and it works.
HOWEVER, I have a customer trying to use servlets, and they are apparently not working. I enabled his domain for use with JSP, and in looking at the httpd.conf file here is a sample of his virutal host section (notice toward the bottom):