Shellye,
A good source for the many questions you have with installation is your host provider. I spent much time on the phone with my host technical support who gladly walked me through the upload.
You can work on a WP site but you can't transfer the domain from your other site or else you will lose that site. You can work on your new WP site using the IP address. Again, a good source for doing this is your host technical support.
Once you install and work with WordPress I assure you that you will be glad you did. If you use a site builder site, you may have problems later (I did!) because you can't transfer the site to your host. Everything has to be done manually. Also
SEO is better with WP as you have more control.
It may be a learning curve and if you decide to take on WP, it might become an additional service you can provide to clients.
Janine