My concerns are:
1. Is this a crazy idea, that is being involved with a married woman? Should I give it a try, having a monogamous programming since childhood? I really like her.
If you are comfortable with the idea that you are not going to be her one and only and willing to make it work, then give it a chance. You may enjoy some of the benefits of being poly. But if you are hardwired to monogamy, it may be difficult to grasp the concept of sharing her, sharing her time with someone else, and not always being "first" in her life.
2. How do I know that she is not cheating or that they are really in a consensual non monogamous relationship?
If she and her husband are truly poly, there is nothing wrong with asking to meet the husband. This would take away the thoughts that she is not cheating or doing anything behind her husbands back. Plus you won't have the fear that the husband might show up at your door one dayf or messing around with his wife. If they are poly, you meeting the husbad will give you a lot of credibility in the relationship and more support in all those involved.
3. Perhaps, part of my concern is the awkward feeling, like, will i get into trouble in dating her? I mean legally or getting into trouble with her partner
Can't say legally you could get in trouble, not a lawyer. But, if all involved (you, the husband and the woman) are all consensual, there should be no issues. If she is cheating or doing it behind her husbands back, that could be a whole different story!
4. Are there guidelines or etiquette for dating a married poly woman? any links or references or experiences or advices?
There is a ton of links and information out there. Being respectful to their relationship is very important, and the husband will be also. If there is any connection or friendship between you and the husband, even better. I have always been friends with my wifes partners. We often all hung out together, had drinks/dinner together and even once went on vacation together.
5. If ever I could pull this off right, what are the chances this will work? Any cases or similar situations you know of? I mean Im a single guy and they are a married couple. My objective is to make this into a long term relationship if possible, not just a fling.
I've never been the "single guy" in this situation, always the husband. Respect for everyone involved can make it work. If the wifeis seriously looking for a poly relationship, it could become much more then a fling...Good luck, if all goes well, it can be a great thing!