Question 4: having experience with secure certificates, if you really want to lock down parts of your site, I would suggest a name brand certificate, like GeoTrust, Verisign, etc. I have discovered that some browers (Netscape and Safari) have problems recognizing the cheap ones (goDaddy) or newer ones. This will be a turn-off to your visitor/shopper. Of course there are hosting plans with shared SSL, but be prepared to pay a bit more for the service overall.

Installation will require a few hoops to be jumped through, depending your host and the certificate, but really isn't a big deal.