Are there any differences between olympic style judo and traditional judo?
What are they? Are they big differences? Are they both equally effective for real situations?

I know a dojo in my area - like 10 min away - headed by a Judo medalist in olympics. Should I go there or is olympic judo too sporty?

If they are an olympic medalist you ought to be good no matter if they're 'traditional' or 'sportified'. An olympic judo medalist could hold their own in a fight any day of the week, and if you don't believe that just try throwing a punch at one of them and see how you fare. When you're out of the hospital tell us how it went.

I'd say go ahead and train as you are likely to learn quite a lot. Just make sure they're legit, if you can't find proof they won a medal they're probably lying.