Do i have head lice? is this gross? if i do have it how long do i stay home from school for?

K, EWE, my friend so generously invited me to come over for a sleep over, so i thought that would be really fun considering I had NO idea she had HEAD LICE. i found out she had head lice because, i went into the kitchen and she had lice shampoo bottles on the counter and i was like, um you have lice? and she said i used to but its gone now, she only had 1 treatment so i dont beleive its gone. anyway. so do u think i have it? and also what should i use to get rid of it? how much does it cost? SHOULD I SHAVE MY HEAD!?!?!?! :'( should i be grossed out because i totally am.