Paradox MG5000 to PC how to

Hi there, I have a Magellan MG50XX series model board witch used to be linked with an alarm central in the past. Now, I don't pay anymore for that service and the IP expansion is pretty expensive (Around 200$). What I would like to do, is that the alarm system talks directly to a PC and then with a program that listens to it, could call external scripts such as powershell to send emails or do whatever I want. Is there a way to make such things? I am an experienced IT and programmation guy but have very limited knowledge of electronic. Lets say I could pass from the phone cable to RS232 (DB9) and listen to the port for events or alarm trigger. Any help would be appreciated.