It’s not clear why you can’t just pick up the phone and call or simply send an e-mail. My suggestion is: the more personal the better. I would call. Be prepared to leave a message. Write out exactly what you want to say. Ask the person for a 20-minute informational interview about the company.
Just in case:
If your relationship with this person ended poorly and you were at fault, call and apologize. Admit that you were an idiot, irresponsible, or whatever the situation calls for. Most people won’t argue with (or reject) an apology that includes the words “I was so stupid.” Then let this job opportunity pass. The last thing you want is for someone to think you’re just being nice/making contact because there’s a job opening involved. (Otherwise, years have passed, and you still haven’t changed.) Then contact your acquaintance if there’s an opening in the future.
Good luck!
(I think that was a whole 3 cents.)