Hi there - welcome to the board!!
This really is a great place for good information! Whatever you need, someone usually has an answer for you!
I didn't take that test - I took the NLN test. Vocab was my weakest section every time (took it 4 times). I'd say if Math is your weakest section, focus on that. I'm not sure how the vocab part is, but for me, it was difficult...reading comp is what got me through I think! And you said your taking an all day class to prepare? That should help!!! If you have a study guide for the HESI, I would imagine whatever is in there is closest to what you will be taking.
Don't let stress get to you. Go in there and breath...tell yourself you'll do fine!!! I was nervous the first time because of the "unknown" of what would be on the test, but each time, I got less and less nervous and I think that worked to my advantage. You will have done all you can up to that point as far as studying...the rest is up to fate!!!
And if you don't pass the first time, take it again when you can! Don't let it stop you from trying!!! You'll get there eventually!
Best of luck and let us know how you do!