Trish,
My answer to your question is that, maybe because DH and I married in our forties, and had lived together for three years and already came to agreement on many things before marriage, I don't feel I need a marriage course or seminar. When something is bothering either of us, we discuss whatever that is and come to an agreement. We work at the same place, although in different areas. We eat lunch together every day and talk when we do. When we get home at night we share what went on that day. If something is bothering me that I haven't mentioned because even though it's bothering me I think it's trivial, he can tell and will ask me if I'm okay. I do the same with him.
Every marriage is different so I don't know how you can really learn about "marriage". One person's expectations of marriage can be so different than the other person's expectations. That's why communication and groundrules and really knowing one another are so important BEFORE you get married.
Then once you are married, I think the key element is to nurture the relationship. To me that means making your partner the most important thing in your life. It means giving that person your respect. It means being willing to be unselfish but it DOES NOT mean being selfless.
I don't need someone telling me in a seminar what they think. I need to communicate every day with my partner to know what he thinks and he needs.
Anyway, this is MHO. Again, other people probably have differing views.
P.S. I can't see having a relationship with another man the way I have with DH but I also can't say whether I would or wouldn't remarry because after my first marriage I was certain I wouldn't, and I did. I just cannot see anyone else measuring up to DH. He would be a tough act to follow. That's for sure!