Usually if you are Vice president you will take over. If the Vice president is unable to take over the Speaker of the House will. Then if he cant take over the President pro tempore of the Senate will then the secretary of Defense and so on and so on... So i am pretty sure it would just go to the vice president regardless of his previous time served. After all the purpose of the vice president was originally to take over as president should s/he die.

*Be aware i am not a Historian so take everything i say with a grain of salt as im only recalling the knowledge i learned in class

Thank you for your question, but it's really not appropriate for /r/AskHistorians. It is not about history at all, for one thing, and is entirely speculative besides -- both of these disqualify it from being acceptable here.