First of all, it's normal that a new Linux kernel package is installed in addition to any existing kernels. That gives you an additional entry in your boot loader. Once the latest kernel works for you, you can erase older kernel packages:
rpm --query kernel to list installed kernel packages.
rpm --erase kernel-VERSIONHERE to erase an older version. That removes the LILO entry from /etc/lilo.conf automatically, too.
Which other packages are duplicate? It's possible to erase duplicates safely. But I would need to know details. If you don't mind doing some reading,
man rpm has the documentation.
Apt-Rpm is not included with Red Hat Linux. So be careful from where you fetch your extra software. Red Hat Linux extras provided at
http://fedora.us are known to work.