I have a question about my Network Engineering Stack Exchange post: Need recommendation for VPN router features
I was mainly asking for protocol recommendations. Please direct to me the appropriate forum.
As I wrote in the comment to your question, you could try to ask the question on Hardware Recommendations.
For something like you want, I would strongly urge you to hire someone for a couple of hours to set this up for you. Since you don't know how to get a cert, This is probably something you should have a professional do. Doing it incorrectly will leave you wide open, even if it looks secure to you.