apt-src unmet dependencies

Hey experts,

We have an Ubuntu 8.04.3 LTS server with plesk control panel installed.

I need to recompile apache in order to increase the value of file descriptors.

During the recompilation procedure I have to install apt-src by issuing the following command “apt-get install apt-src”

But when running this command I am getting the below error

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Reading state information... Done
You might want to run `apt-get -f install' to correct these:
The following packages have unmet dependencies:
  apache2: Depends: apache2-mpm-worker (>= 2.2.8-1ubuntu0.14) but it is not going to be installed or
                    apache2-mpm-prefork (>= 2.2.8-1ubuntu0.14) but 2.2.8-1ubuntu0.11 is to be installed or
                    apache2-mpm-event (>= 2.2.8-1ubuntu0.14) but it is not going to be installed
  apt-src: Depends: libapt-pkg-perl (>= 0.1.6) but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
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But as you know 'apt-get -f install’ can remove essential packages needed for server functionality and in the past it caused lots of problem for my plesk application.

Is there other method to solve this problem without using 'apt-get -f install’????