Ebook download with autoresponder - which way to go?

Hi,

I'm not sure if I'm allowed to mention company names here...

Apols if I'm breaking any guidelines - I'll happily rewrite the post without company names, but the names are kind of relevant...

mailchimp has a free option, so long as the number of emails sent out is below a certain level -- i want to know if mailchimp would suit what i need to do or if i'd be better off with aweber or another option:

i want to add a form to my wordpress site so people can enter their name and email to get on my list and to get a free pdf of the first few pages of an ebook. once they're on my list they'll get a series of emails as well.

and i want people to be able to choose a different form (on the same wordpress page), to get on my list and pay for the full ebook. these people will also get a series of emails.

the emails people receive can be the same for each group of people. Or (better) the people who downloaded the free option will also have a few words encouraging them to get the pay-for ebook.

And i want people who got the free pdf to be able to come back and get the pay-for ebook -- i want it to be so that person doesn't start receiving the emails from scratch again - but continues in the process from where they were.

can i do this with an autoresponder system?

is the free option on mailchimp going to give me this or something like this?

or is there a better way of doing what i'm trying to do here?