I did it in 2008, I have to say it was probably the hardest one day race of my life. I’d come from a fairly good road and time trial season and had also spent a week in the alps a few weeks before the race.
I think one of the big things is to make sure you are happy shouldering the bike for extended periods (10-20 minutes) for the first climb. My whole body but particularly my fingers were cramping on the last descent making braking difficult (but that was with cantilevers).
I’ve only done it once and would love to do it again but I’m now on the wrong side of the world to make it work.
Good luck, you’ll enjoy it.