How difficult is it to customise NopCommerce?

My customer wants an e-commerce site. I'm a .NET dev so NopCommerce seems like a good place to start but I haven't used MVC or NopCommerce before. I'm keen to learn about them but first I need to quote this job quickly.

The problem is his requirements are quite different to a standard shop site. This is difficult to explain without broadcasting his business idea. A customer will go to the site and chose a "container". This may be a small, medium or large container. The small container costs $20, the medium costs $30 etc.

Each container entitles the customer to purchase a certain number of products. For example the small contain can hold 10 points worth of products. Once the customer has chosen their container, they need to chose products to go in the container. They may add some socks, these are 1 point. Then they may add a shirt, this is 3 point. And so on until they are up to 10 points.

Also, once a container is ordered and filled, the customer needs to be able to enable repeated delivery of this container (say every week) with recurring billing.

I hope this question isn't considered too vague but I'm just in the initial quoting stage of the project it would really help me if I had some idea of how difficult this may be. I'm an experience dev but have used WebForms and WinForms for most previous jobs and I've just had a year off so I'm a little out of touch. Once I've spent some time learning more about MVC and NopCommerce will this be reasonably easy or not? Should I be using NopCommerce or would I be better off building this from scratch or using another framework?

MVC does have a bit of a learning curve, but it's not too hard.  Similarly for nopCommerce architecture and development; see the documentation.
You might be able to customize "Reward Points" to  allow them to be purchased, and then the store handles their use for payment.