It sounds like you might be familiar with your hospital's policy about drug testing etc. It might be helpful to revisit those policies. If indeed the test comes back positive, I imagine, they will report you to the BON. But I emphasize, you need to check the policy book.
It really is a sorry state of affairs, where companies are doing random urine checks. I've worked as an engineer in the automotive field and that is not done in our world, not even for the hourly guys. I did have to submit a hair sample when I first was hired in.
As for question 1, you may not get the chance to quit, if indeed the test is positive. I'm sorry these are difficult questions to answer. But my guess is, if positive, they MAY fire and report you to the BON. Some people will tell you to self report, it looks better. Just go to in work and see what happens from there. Not really an answer but you just to wait and see. I'm sure you're panicking and anxious, normal responses. I know I would want to know right now what is going to happen.
Is the first instance of drug or alcohol use for you?
I'm so sorry for your predicament and can feel your pain. I was in your shoes 22 years ago. was found diverting and was fired that day and they reported me to the BON and my license was suspended for 6 mos. I found another career as a mechanical engineer and have worked in that field since 1993.
Hope everything goes well and if they do report you before you can then get yourself to a treatment center or be evaluated by a therapist to see if you have a substance abuse problem.