That’s good advice especially from ehrob. If you want a bit of a guide I’m sure you could find someone too.
Fitness isn’t quite that simple, road fit isn’t the same- it’s a good base but sustained technical descending needs a different sort of fitness, and the timed stages can be ridiculously physical, the mix of long slow liaisons and shorter, flat out stages is an interesting change.
TBH the SES is fairly full on. I wouldn’t want to put you off, it’s just not an obvious first enduro. Something like a muckmedden event would be a gentler introduction, or even some of the tweedlove ones.
(having said that, I was in at the deep end with one of the first inners enduros, way out of my depth because nobody really knew wtf an enduro was back then… and that whole “barely surviving” thing was a huge part of what made it awesome and got me addicted. So maybe not!)