Custom Product Entry for Custom Orders

I was wondering if this was possible w/ MP? If the title of this thread is not clear enough, let me give you the example I'm using for this scenario.

I have a shop were I sell artwork that's already been made via MP, I have a custom order form that the user can fill out and send for any custom work. Now I was wondering how to create a way to allow the user(s) to purchase the custom artwork after they've recieved a price quote from me.

Then they can go to the shop, click on Custom Artwork(product), read the small details, Add in a few things, for variations, I was gonna add the variations types based on custom artwork (airbrush,drawing,graphic design) provided in their custom order form rather than a refined detail of the actual order.

So this brings me to 3 new questions.

1. If I was able to assign a sku number in my order form(s) with their price quote, is there a way to allow the user to enter the exact same sku number during the purchasing of such a custom product?

2. If not number 1, then can the user enter details of their custom product in a comment area that's also sent with the purchase?

3. Can they specify the price as well on the custom order?