Non EU citizen moving to Romania

Hi I'm Oscar and I'm from Costa Rica. I have a few questions, if you could help me.
Me and my Romanian girlfriend are planing to move to Cluj-Napoca. Could any of you help with any information? She lives and works there already but it's kind of difficult to get our way around the information regarding the matter (for me).

- What papers do I require to move and work there?
- Could I get the resident visa if I go there with a tourist visa first? (I've been there for 3 months last year and I'd love to stay there the next time i visit.)
- I've read that getting married would be the easiest way for me to get a stay visa. But I'd love to be able to get a job as soon as I get there.
- What papers do we require to get married?
- Also could we get married in another European country and just prove our marriage with our marriage certificate upon returning to Romania?

Thank you in advance.
P.S. Excuse the length but I'm really eager and concerned about this. All the best!