FWIW, professionals having to go on a course and get certified in things doesn’t actually mean it’s difficult, it just means they need to demonstrate that they’ve been trained. If you’re working with the public there’s more risk of/from needle-sticks, I’d imagine there’s a bit of training on dealing with phobics too. Basically it’s not the same as doing it for one person.
When I was diagnosed diabetic (at 7) they demonstrated to my mum how to do it, told her to practice on an orange, and sent us home. I learned myself just by watching and started self-injecting at about 8. It’s really not hard and shouldn’t be painful either- don’t freak out! I think it’s better to do it yourself if you can- every so often you’ll get a sore one and it’s nice to be able to stop!