@smason as @Chris_Conn said you are passing in the response as the payload for the request. I am not trying to be rude here but it seems you are trying to jump in with both feet on something fairly advanced that you don’t yet have the understanding of.
Perhaps baby steps are in order first? gotta learn to walk before you can run! Creating a quote on REST or even outside of rest is fairly complex.
I would recommend getting some base understanding off the REST API concept in general and then perhaps use a smaller business object to get your feet wet? For my training I usually use ABCCode to start with using Custom Methods and understanding the mechanics.
Just my 2 cents, I think if you just jump right in you are going to end up making some key mistakes in the process which will require you to rewrite the thing in the end. As they say you are going to have to pay for it at some point, in the beginning, middle or the end.
Checkout the REST Novel
as well as the many other REST Related posts on the site.
Read the Epicor Help in regards to REST that is VERY VERY complete and pretty through
Read up on SWAGER.IO and oData
https://epicweb.epicor.com/doc/Docs/Epicor10_RESTServices_v1_102400.pdf#search=REST
Etc.