Nothing feels better than surviving an offroad race as an old noob; even finishing at the back of the field is so much better than wondering if you can do it.
2 years ago, like you, after reading about others on here, I returned to cross-country racing after 23 years off. Yes, old bodies break easier and take a bit longer to heal, so managing risk and accepting you'll be passed a lot might be part of it for a while. I usually finish and rarely get injured, but I'm now in better shape and can ride more competently than ever before. I'm loving every second of it.
Good to see you've got riding schools in your schedule. Technique and setup will save you so much energy.
In 2 years when you join the 50+ class you'll have an age advantage again!