Setting Up Power Store With SSL Certificate

I am about to order a SSL certificate for the web site where I have installed Power Store 4.01. The store is installed in a folder on the site (ecommerce) I have opted for the secured/dedicated certificate for the domain.com name and not www. The site is hosted by 1and1.com.

I have talked to their tech service department who tells me that all is required is to order the certificate and enter some specific coding into the .htaccess file in the root directory of the site and that's it! It would secure the entire web site and not just the Power Store as I understand it? Is this correct?

I have read through all of the posts that I can find and see a variety of issues some folks have had in the application of the certificate and some code changes to solve these.

Before doing this, I would like to know if there is a downside in securing the entire site which as it has been explained to me, would secure everything on it? I have asked about potential issues with users accessing the site with different browsers and they tell me none! This seems to be too simple to be true, but perhaps it is?

My original intent was to secure only the ecommerce section of the site, but from what I gather from talking to the tech guy, this is not how it works?

Can you give me some direction on this? Are there any known issues in doing it this way? I will be using the PayPal Standard gateway which is as I understand it, already secured.

Out of all the many web sites that I have developed, this is the first one that has required the certificate, so please bear with me as a "newbie" where this is concerned.

Thanks!