That sound like a very good option since you're already acquainted with the medicine. Make sure you also have more SN servings ready in case you throw up right after taking it.
Also, you should read this thread about the documented cases a user compiled for us, pay special attention to the unsuccesful ones, it's also important to be aware that it might not be completely peaceful, although most of the times it seems to be alright.
I have combined and added all the brief summary of all the attempts, assumed successful and unsuccessful, of SN suicide. These are all posts that the member has made to document the method, news articles, and scientific articles. If I have missed any I apologise and it would be great if you can...
sanctioned-suicide.net
Thanks