Are you asking about bridal attire for an older bride, or just dressing in general?
I think a bride should wear whatever she wants at any age, but I would think a more sophisticated look would be in order. A beaded gown, with no train if it is a formal wedding, or a tailored suit if it is casual. Whatever makes you comfortable!
"Since i am now engaged and a working woman, should i dress differently?"
I have no idea what that means--you could be engaged and a working woman if you're 22, or you could be 75! You don't have to cut off your hair or put on a burka because you're engaged. And, depending on the work you do, you may or may not have to dress "differently." Obviously, many workplaces require that you dress more formally than you did in your student days. Some require that you wear a uniform, or wear safety equipment. Then, again, if you work at Hooters, the requirements may be different.
Dress for the occasion and dress for your own body. I've read that women over 40 "shouldn't" wear sleeveless--obviously, Michelle Obama didn't get that message, and she looks fabulous with no sleeves. If your arms are fat and flabby,cover them--even if you're 12! OR, if you don't care, DON'T cover them. You're the one who has to feel good in what you wear.
As for the latest trends, you can be trendy at any age, as long as a look flatters you. Again, if the look is wrong, it's wrong, whether it's classic or trendy. For example, I look lousy in crew necks and better with some skin showing. It doesn't matter to me what the latest trend is--if the whole world is wearing crew neck sweaters, I'm still going to look lousy in them.
My own policy is that if I'm going to spend big money on major pieces, I don't want them to be in and out of fashion in one season. I buy classic and neutral. If I want a "trendy" look, I'll go off to H&M or buy something on sale and throw that into the mix. If I wear it for a season and it's "out," okay, no big loss.