I did that, too, at age 46, 24 years ago.
The number one key to comfort was learning that there are thousands of others doing the same thing...men and women.
And, that you bring with you a vast field of life experience that enlarges and eases your understanding of the classes taught.
I thought I would be the oldest person in the school...I wasn't. I also thought I should keep quiet because everything I had done was 'learning by doing', and that I probably had it wrong, anyway. Not so. But I didn't see that until the end of the first semester.
You'll find that you don't speak up much, but when you do, you'll have something valuable to add.
Instructors notice. One instructor (computers) told me that he had a seventy-year-old at night school who just couldn't 'get' the meanings. The man wasn't interuptive, but the instructor could see that puzzled and 'struggling' look on the student's face.
The instructor taught as clearly and slowly as he could, but eventually had to go on, hoping that the gentleman would catch up to the others.
One evening, the instructor must have said something this student 'caught' because teacher saw a light bulb go on over the gentleman's head. A big smile spread across the elder's face.
I'll never forget the instructor's face when he told me, "That's when I knew I was a TEACHER."
Good for you for daring to enter a new world!
It's an adventure...one you'll never forget.
Read the book, read the book, read the book. And remember that each chapter likely contains only one main point, fleshed out with lots of background material.
Study as you go, and know that it takes at least 18 hours for information to 'stick' in your head. 'Cramming' the night before an exam doesn't work.
See if you can pick out the main point of the chapter, early on. The details will fall into place. Don't sweat them.
And, age doesn't count in the lunch room. Students of all ages always gravitate to someone who 'gets' the current chapter.
Enjoy! (I feel a little envy.)