iphone email/sms/incar

Just had confirmation of Vodafone cancelling my contract in a few weeks time and i'm quiet set on getting the iphone.Just a few questions that want to clear before taking out the 18month contract.

I have both yahoo and a goolemail account,does the iphone combine these emails into one account or will i still be able to view them seperate?

When typing a sms message does it count how many characters have been used/remaining as when i had a look in the apple shop i couldnt it anywhere.

& might sound a stupid question but when the ipod is connected to play music through car speakers does this also act as a handsfree/does the conversation play through if call answered?