I'm 34, will be starting a degree this September and I'm currently nearing the end of a 12-month Access to HE course.
My education background was I achieved fairly mediocre GCSE's (3xB, 6xC) as a very unmotivated teenager, went on to A-levels where I was doing ok but incredibly unhappy. So I dropped my A levels and began a BTEC in music. I failed the first year of that and dropped out half way through repeating it.
Fast forward 12 more years and a string of fairly uninspired jobs and personal projects later I found myself as an inside sales rep for a paper merchant. Mostly content but not feeling any aim in life. I decided I needed to mix things up so while I was still 30 and eligible I applied for the working holiday visa for Austalia which I did between 31-32. Best year of my life to be honest and it was where I made the decision to study again.
And it's the best decision I've ever made. Nothing gives you a better appreciation of education like time spent in jobs that only require soft skills doing monotonous, unchallenging work for modest pay. If you're going to be doing a subject you have a passion for, the varied challenges will give you reason the get up in the morning. The worst part of my week is the weekend as I still have to work part time. Come clocking off time on Sunday though I can't wait for class to begin on Monday morning.
My college workload is typically 30-40 hours per week, about the same as I'd expect a degree to need at a minimum and it's quite manageable so long as you aren't working excessive hours in any employment (I do 22.5 hours). There are times when I've let things slip and had to rattle off an entire assignment on its due day which is still something I need to improve on, but staying on top of the work, getting the grades back, and having a general sense of achievement is a great motivator.
The age disparity isn't a big deal, I'm on a course with mostly 20-25-year-olds and save for some friendly banter I forget there is an age gap most of the time. But I have a distinct advantage in being willing to speak up when there are issues.
If you know what path you want to take and you have no barriers other than self-doubt then you need to just be a bit more confident in yourself and go for it. By 31 I would imagine you've probably been through several jobs at this stage. Each one you've had to learn new skills for. For me when I start a new job that's the only interesting time while learning to do it. Once you settle into being competent it becomes boring. Education is like a constant flow of that new interesting period where you gain a competency then move onto learning a new one.