In my diocese, yes, a Marriage Preparation course is necessary for people who want a Catholic wedding in a Catholic church.
My wife and I went through it umpteen years ago and it wasn’t bad. Before taking it, we didn’t know what to expect, and I was somewhat irritated; I thought it was just a case of the diocese buying into the bureaucratic nonsense craze that seems to be taking over the country (force people to take a course AND charge them for taking it–yay another fundraiser!). And we expected it to be heavy on the dogma.
But to our surprise the course was very non-religious. Each evening a different speaker would come in and discuss different topics: the raising of children, financial planning, etc. And each couple would then take some time to discuss the various aspects of that theme for the evening. It turned out to be a very enlightening process.
You’d be surprised how few couples discuss some of these topics before they get married, and these issues are usually the ones that cause break-ups afterwards. Everybody is so wrapped up in the infatuation with each other, or they want to rush into marriage because they think if they don’t they will lose their resolve, or they don’t want to bring up a touchy subject because they don’t want to risk offending their partner, or whatever. It is one excuse after another. But it is better to address these issues before marriage than wait until later when it turns into a much bigger issue.
For example, if one partner would like several children but the other only wants one (or none). I can’t believe how rarely this conversation actually takes place.
Or money issues. One partner is much more self-disciplined than the other. Sooner or later the spendthrift is going to cause some major issues, so it is better to bring up these differences now and discuss how they are going to be handled.
If you want a Catholic wedding, don’t worry about the course. Go through it and work through the material honestly (do not just give the answers you think your partner wants to hear. If you are already being dishonest and caving in to a partner, those are two issues right there that will blow up later–among others that may come up ).
Make the best of the course, and try to have some fun with it instead of treating it like a chore.