Do it mate!
I'll be there for my first ever sprint too on the 17th, I'll be in my Skyline.
Sounds like you've got all the boxes ticked to pass scrutineering, just make sure your battery is secured and you've got your coolant overflow dumping into a bottle, not the ground. Even if you've missed something there will be lots of friendly people there to help you out to make sure you get out on the track The whole "secondary method of securing the bonnet" is a little meh sometimes. Pack an old belt if you havn't got something else already . I'm pretty sure though that you don't need anything unless you've got an aftermarket bonnet, I know I've never needed anything.
At the end of the day you're not racing against anyone else, just against the clock, and that's still heaps of fun But when you're out there you'll be matched with others of similar driving calibre.
You'll need a blue triangle, not rectangle, lol, the sides need to be 150mm long, just use blue electrical tape or contact like you'd use to cover your old school books
If you're really anxious about it you can come round to mine on Friday\saturday night and we'll give it the once over and spin a few yarns with you. My housemate is also a Sprint virgin like you and will be taking his skyline for the first time too.