After finding out my girlfriend was cheating on me, I kicked the windows and roof out of her car. Problem was she was inside of it at the time. I paid for the car to be repaired through my lawyer. I plead guilty to mischief under and got a conditional discharge. I was sentenced to 18 months probation and had to complete the PARS program. My lawyer said when I completed these it would be as if it never happened. However my PO says that something will always be on file. On my probation order, I have basically no restrictions. Will I have any problems leaving the country now or when I complete the probation and will there be any point of me applying for a pardon? Any advice would be greatly appreciated.

This is a tough one,
1. there is always "something" on your record any time you are arrested and appear in court, this is available for police and law enforcement and national security. Even a pardon will still be on the record and show that it is a charge and a pardon.

As for as travel outside of the US, you will have to qualify for a visa from the nation you wish to visit,
I don't see this crime being a issue