A., I'm a retired police officer and have some experience in this area. Some orders state that the papers have to be served by a process server while others can be served by anyone. If it says they are to be served in person it means just that. Certified mail will not work.
All counties have process servers. You could contact the Civil Division of your local Sheriff's Office (the Sheriff's Office serves cvil papers in my county.) or the court and they should be able to give you a phone number for the court in Pennsylvania. Or you can call the Sheriff's Offic or the courthouse in the county in which your ex lives and they will tell you who to contact.
If you ask they will also explain the process to you so that you'll know what is going to happen.
There are also private process servers. I'm not sure how to find them. If you were working with an attorney they would have one or more in their employee. And a local attorney could have a contact in PA. But I think this route is more expensive.