HTTP Error 500 when browsing homepage and admin

[seasheps]

I can no longer see my website, nor admin page: http://glovedup.com/zencart/
http://glovedup.com/zencart/adminurrhtcqq/index.php

This afternoon I attempted install of Zencart Addon: Newletter Subscribe v 2.1.1

When I realized the add-on would not work on my version of Zencart (1.3.9) I tried to replace all original files.
Site is hosted on Godaddy

All the time I was doing this I was viewing the website and Admin and all was OK.

Four hours later when I log back onto internet, I can no longer view the pages.

Godaddy say I have to solve this problem myself.
I honestly don't know where to start - can anyone advise?

[Donal]

what files did you try and replace?

[seasheps]

There were quite a few, I'll get a list together.

admin/index.php
admin/customers.php
includes/functions/function_email.php
includes/functions/audience.php
includes/modules/pages/account_edit/header_php.php
includes/modules/pages/account_newsletters/header_php.php
includes/modules/pages/unsubscribe/header_php.php

I realize this was a silly move on part - I'm new to zen cart and php

(this is not all the files, but main ones)

[Donal]

A lesson in backup i think

Its gonna be difficult with that many files altered
what stage is your site at?
have you many mods or editing done so far?

[seasheps]

Its a new site, so not active yet.
I've spent several days, tweaking it and I guess I can start again, but my goodness, I'd like to avoid that.

There weren't actually that many more files than those already listed.

Most of the files uploaded were additions and not in original installation.

Is there anything I can do before starting again?

(thanks for your help by the way)

[Donal]

If by tweaking you mean at your template files you could always save them assuming you used the override system.

the only other way to go is a process simalar to an upgrade, other wise your just stabbing in the dark at this point

btw

Godaddy say I have to solve this problem myself.
I honestly don't know where to start - can anyone advise?

dump godaddy :)