My price is €250 ( excluding Freelancer.com project fee ) and 7 days time to complete the project.
I think Chrome extension will be a good solution for your requirements. Since a am proficient in Chrome extension developing, I will go with Chrome extension developing, not executable file.
There is very little possibility that Facebook changes will break the extension execution, but if it happens it will only take few minutes to adapt the changes, i will handle it in future if you want.
To be honest, nobody can guarantee you that their script/app will work if Facebook changes API, only they can guarantee you that they will adopt the changes quickly, which i am offering you.
Let me know if you want to discuss more.
Best regards,
Mohammad Apel Mahmod