To answer your question:
It is my understanding that changing your membership does not instantly give you 70 connects, but it DOES give you the ability to begin purchasing connects immediately.
You will receive 70 connects (instead of 60) at the time that your connects normally roll over.
(If this isn't the case, I hope someone will correct me.)
Don't do that.
Buying connects is not the way to go. It is not the path to success.
If you ran out of connects, then it means it is time for you to work on improving your skills, work on improving your profile page, and work on improving your portfolio.
If you upgrade to Freelancer Plus then you will receive a prorated amount of connects based on the day of the month. Also, he's right about purchasing connects. It's not the way to go at all, and it is really there to deter people from abusing the system.
I would upgrade as soon as possible and use this down time to focus on improving your skills and personal branding.