Go for it. Another thought is that often you can just attend the lectures without paying. That may be all you need.
Any time there is something available you want to learn, I say, Go for it! But, if it were me, I would audit rather than put myself through the whole course. After all, it's not like you are going to open the newspaper job ads and see, "Ancient Historian Wanted." Since there is no point in paying for credit, I would just attend lectures and follow along in the text book.
If you download bittorrent (www.bittorrent.com), you can download a lot of textbooks for free. If you'd rather have a teacher, that's different but you can also just download the texts and use your laptop for class to save money. I know other students who do the same thing :)
Why shouldn't you? Go for it. The toughest part will be walking into class for the first time. But I know from experience that your lecturers and tutors usually enjoy having a mature person to teach for a change.
IfII am still compos mentis when I retire, my ambition is to do a history degree. Don't have the chance right now as I am working full-time.
Go for it, if you can! (turning green..)
When I was in college there were some excellent history professors who gave great lectures. I didn't sign up for the course, I just went to lectures and enjoyed them.
Just go do it!
Why on earth would you NOT?
If you've got the time and money, why not?
Yes, it would be fun!