Simple questions for develop theme

Hi:

I'm developing a new theme, but i have some questions:

1. I need create menu, I found in documentation:

http://docs.whmcs.com/Editing_Client_Area_Menus

http://docs.whmcs.com/classes/classes/WHMCS.View.Menu.Item.html

But too I need know in which file I create menu with API methods?, I write this functions in header.tpl?.

2. For default, WHMCS have some pages:

domainchecker.php to buy domains

cart.php to buy hosting

etc.

But I need create new pages for other products/services: VPS, dedicated server, maintenance service, etc.

How I do this?, because I created new php file and insert the product/service in code, but WHMCS panel haven't price and the client cannot buy.

3. I need optimize SEO to my pages, for this I need change name to files:

http://www.mydomain.com/domainchecker.php rename to http://www.mydomain.com/buy-domains/

http://www.mydomain.com/cart.php rename to http://www.mydomain.com/buy-hosting

etc.

I can do this since admin panel?, or I need rename from .htaccess?.

4. If I create new php file, for example "custom-functions.php", how I load WHMCS core to access her functions and variables: http://docs.whmcs.com/Template_Syntax

Thanks very mutch.

Please, any reply?, this is very simple questions.

I need any reply, this is very simple questions. Any professional can solve my questions? thanks.

You need rename from .htaccess thats the best solution