dependency, sudo, and apt-get errors in Kubuntu

Question

It's been awhile since I've used my Kubuntu system. I'm trying to upgrade to version 16.04 - and running into a series of problems:

1. When attempting to upgrade Kubuntu to version 16.04, I get the error message:

   Required depends is not installed
   The required dependency 'apt (>= 1.0.1ubuntu2.13)' is not installed.
   

2. So, when I attempt to fix that in the (Konsole) Terminal, I enter:

   sudo apt-get install --only-upgrade apt
   

   The response that I get is:

   Command 'sudo' is available in '/usr/bin/sudo'
   The command could not be located because '/usr/bin' is not included in the PATH environment variable.
   sudo: command not found
   

3. I then try to fix that by entering:

   apt-get install sudo
   

   The response that I get to this is:

   Command 'apt-get' is available in '/usr/bin/apt-get'
   The command could not be located because '/usr/bin' is not included in the PATH environment variable.
   apt-get: command not found
   

4. I tried to address that by entering:

   export PATH=/usr/bin:/bin
   sudo apt-get install --only-upgrade apt
   

   In response, I get:

   E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
   E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?
   

5. In order to identify what might be causing the problem, I ran:

   ps aux | grep apt
   

   The only thing that comes up that looks like it might be a possibility is this:

   4381  0.0  0.0  11740   936 pts/2    S+   23:50   0:00 grep --color=auto apt
   

(All the other "apt"s it finds are part of "caption"...)

At this point, where should I go? What should I try?