I'm not too sure where that leaves you sweetdreams, but I was in this situation recently. I discovered that I wasn't actually afraid of 'being dead' because being afraid requires conscious experience which ceases to exist after you die. But I was definitely afraid of the process itself, to the point where I was devising all kinds of ridiculous ways to put myself into a dream state as I died, or recreate the experience of 'walking into the light' (the research on the neurology of near-death experiences is fascinating).
In the end, I sat myself down, wrote out my worries - what was I actually scared of about the process. Then I did my research and thought about each of my fears scientifically and I figured that actually, with some basic precautions I could have a really pleasant and painless experience and leave my body in a nice presentable state (both of which were important to me).
So perhaps that is what you need to do. Take a moment, mentally run through the process in your mind or act it out but just take some water instead of the SN and then lay back and think about your emotions - as you're laying and waiting for it to 'kick in' what are you afraid of? Is it that it won't work, or that you'll be sick or feel intense pain, or that everything will suddenly go black?
Once you know exactly what it is that you're afraid of you might discover that it's actually a whole lot less scary than you imagined, or perhaps it's something that you can work into your plan and reassure yourself. Either way, I think it's worth holding off the actual act until you've dealt with your fears - much better to delay just a little bit to make absolutely sure that you're ready, and have your final moments be calm and peaceful rather than laying in utter terror.
Either way, wishing you peace and wellness