Some questions about using google for email

I am thinking of switching to gmail for my email. My primary reason for this is not because of server downtime but I wish to use some of the features. I was hoping someone could answer some of the questions I haven’t been able to find answers for.

  1. Apart from a custom email address whats the difference between hosting my email with gmail and dreamhost. I mean once I log in does it look like a free gmail account with ads and google branding or do they strip back on that?

  2. Do the spam assasin configs Ive set up with dreamhost still apply to emails or are they forwarded directly to gmail? I know google is pretty good on spam but I guess i want to know if im still going to have to log into webmail to tweak spam assasin configs.

  3. if i already have a google account will this new address interfere with it or are the dreamhost addresses considered seperate to google accounts? (I dont really want to have to sign into my existing google account after checking my dreamhost email)

Hopefully fairly easy questions but i couldn’t find any information about them in the forum or wiki.

Would appreciate any comments. Thanks!