Setting up Multisite to sell two services...

Hi

I am completely new to Wordpress Multisites, however I have been using Wordpress for many years. I have read several guides online but I still cant quite get my head around how to implement what I would like.

I would like my multisite main site to the be the ‘shop front’ to sell the following two services:

Sites and/or Blogs
Shops

When a user signs up I would like them to choose either one as each is differently priced. Once they have chosen and signed up I would like to give them a two week trial and if they don’t upgrade to the paid account after that time their site/shop is disabled and eventually deleted.

I would also like the plugins and themes to change depending on what the user has select (i.e. Shop, blog or site).

Is the Pro Sites plugin the best or the WHMCS plugin (I own a WHMCS licence)?

I would also like my main site to be a social network using BuddyPress, however can you have the user automatically signed up for an account on buddypress when they signup for a product (site/blog/shop)?

Any idiot guides would be greatly appreciated.