It's definitely still possible! If this is something you really want, don't give up. It may take a long time if, like vhab said, you're only taking one or two classes at a time. Really, you need to look at the required curriculum, and see how many classes you have to ultimately take, and what the schedules of those classes are. How can you fit this into your life, as it is now? Are you a full-time student, or are you working full-time? Or are you somewhere in between? This will help you figure out how long it will take you to get it done. But hey, anything is possible! There are definitely examples of people get into different types of engineering after having careers in something else.
Also, at 25, you're not that old! You have a lot of life left in front of you!