A reseller account would be the way to go. Yes you can get a certificate and have it installed before making it live. You will have to provide the domain name the certificate will be used for and will have to test it using an IP number. Besides warnings there should not be a problem.
The only way you would be able to do this is with an upload script where they upload through the browser.
Check hotscripts.com for an upload script ot you can try this one.
http://www.perlscriptsjavascripts.com/perl/upload_lite/
It shouldn't take too long. But if you have questions about it please open a ticket with the help desk (link above) and I am sure you will get a better answer.
The mods do not have access to the servers or your account info and the techs don't frequent the forums.
Welcome to the forum, Mike
Open a help dest ticket to support and see if they can reload the FP extensions. If it still fails, look for some other way to process your forms. There are many available like DodosMail.
Well here's a tip. If it was working and you didn't change anything and it is now broken that would warrant a trip to the help desk. Now if you made changes that may have caused the error then I'd try to figure out what you did before going to the help desk.
I didn't mention the option of another domain name. Sounds like the content is already on the TCH servers and just not working as it should because you are accessing it with the IP number.
You can purchase another domain name and park it over the existing domain name (by opening a help desk ticket) you bought the hosting for. Then just access the site with the new name until you switch the DNS on your old host's site.
When you are satisfied everything is working switch the DNS for your main domain name.