I need help to sell via my emails, I'm stuck

Hello there friends!

Thank you in advance for reading this inquiry of mine.

I have created my squeeze page, all is well people are subscribing. I'm teaching people how to build private blog networks and I'm starting out giving away the guide, the first chapters of the guide in the first emails.

In my 3rd-4th email when the most important chapters kick in, I send them to my sales page so they can get the full guide. My questions are...

1. Since people have already read the previous chapters would they buy everything again just to get the remaining chapters?

2. I do this (giving away the first chapters) because I want to prove them that know what I'm talking about. But maybe this isn't the correct way to upsell?

I still haven't got enough stats to see where this is going and I should wait, but still, would you pay for something to get the remaining 60% ? Do I give away too much? How can I redirect them to the sales page without them think "damn he's now asking for money, up to the half of the book it was free!"

3. What's a nice technique to make someone pay for something when he got used to the first emails being free?

Hope I make sense! Thank you!