Using MarketPress and Multi-Site, want to have a "more complete", filled out template for

I'm fairly new to WPMU, but familiar with Wordpress... Just built a WordPress / MarketPress / FrameMarket / GridMarket multi-site installation at (it's not done yet, still prototyping).

What I'm trying to figure out is exactly how a new child site is created when someone registers. I believe I've successfully got the children sites using GridMarket (did that by deleting all other available themes).

Now I'd like to do 2 things:

1 - Want to have new sites when they are created be completely filled out with my template data: specific pages, specific menus, sample products, etc. Assuming this will involve setting up a sample site somehow, with sample options in GridMarket, and storing those wherever register.php gets it's data? Any tips/tricks on this.

2 - Would also like to limit new sites ability to change some of this sample data. For example, would like to have sample pages and sample menu items that customers can NOT remove. How best to do this? Is there a plug in that limits access to some of the admin screens?

All help appreciated. Thanks!