Well done @taz911 and yes, You need to subscribe for Off road club membership, either Monthly or annual is your choice depending on your longterm interest:)
as regards joining drive, You can get a confirmed slot to any one, either 23 or 24th, and also add your self add WL to second drive, and if there is any availability left by Thursday, You will be added to second drive also by drive lead. The choice is urs which one you want to go for. Like this there is no restriction on No of drives you do in a week ( as long as you fit for the drive depending on your rank with Carnity)
Regarding any additional Prep, once you RSVP the drive, the details are mentioned what all is mandatory to get along.
Looking forward to see you soon and welcome to this amazing passion:)
DP