My condolences to you and your family while working through your mother's passing. I imagine the process of identifying items, their value and then attempting to sell them in today's environment might be a bit challenging. I recommend that you take a look at a website known as Longarm University - it's a site where folks post used longarm machines for sale. You might gather some helpful information there in addition to talking with your mother's favorite gal at the dealer. Best of luck to you all.
Here is a link to the site -
https://www.longarmuniversity.com/index.html