This sounds like something that could be done by an Arduino in the hands of someone with suitable knowledege and experience. For someone without knowledge of electrics, electronics and programming it sounds like it would be the equivalent of learning to swim as your boat sinks in the middle of the Atlantic.
Another important thing to consider - even if you do get it to work who will be able to maintain it if you are not available due to vacation or illness?
These are some of the reasons why commercial systems appear expensive at first sight.
My main recommendation is "pay for a professional repair or replacement system"
IMHO there is zero chance of getting your system to work by modifying existing programs - even if you could find some code that provides a starting point - unless you (and preferrably a colleague working with you) acquire sufficient programming skills so that you would not really need any code to start from. There are just so many small ways in which your system will be different that you will get tied up in knots.
If you do want to pursue this project my suggestion is to start by identifying small features within your project and learning how to do each of them on its own. There is a wide range of examples with the Arduino IDE and I suspect most parts of your project will be covered by them. This will likely take several weeks of part time study.
You will also need to learn how to interface your real-world equipment to the Arduino.
Sorry if this is not what you wanted to hear.
...RPlanning and Implementing a Program